How to change Transmission Oil and Filter in the 722.6 Automatic Transmission W140 S-Class

When these transmissions came out, Mercedes marketed them as sealed for life. Turns out they need transmission oil change after all. Of course this is the case when it is vented with the atmosphere and components have wear over time. If you have passed 100.000 km which is very likely for cars of this age, then go ahead of changing the transmission fluid ASAP. Also if your transmission starts feeling more jerky than usual, then change your transmission fluid ASAP.

If you notice late shifting or if it hangs excessively on gears during revs, or even slipping, then it is possible something else that is the issue. There are so many stories around on the internet that changing gear fluid will ruin your car. This is utter bullshit since changing transmission fluid must be done as preventative maintenance. There are some cases where changing fluid will not help save your transmission, because excessive wear and damage have already occurred. Do you see the difference?

Weird shifting and limp mode can often be the result of a failing conductor plate in the 722.6 transmission. This a known failure item and can be changed by yourself. The conductor plate is the electrical connection inside the transmission, which connects the signals from the computer with solenoids that steers the valve body shifting mechanism. Replacing the conductor plate is not covered in this article..

Note on slipping gears

Worst scenario of all is when the transmission is slipping on the gears, which is most likely due to worn clutches. If that is the case the transmission would need a rebuild with new clutch plates. Changing transmission fluid will not fix this issue, and the slipping most likely will get worse afterwards, since the new oil will not contain transmission debris and the clutches will slip easier. Keep in mind the oil change did not ruin the transmission, the transmission was worn out in the first place and total transmission failure is just around the corner.

Preparation

When changing fluid, you will need more stuff than just the oil. Mercedes used a special automatic transmission oil in blend in the 90s, which was supposed to be sealed for life. Turned out that this was not the case and you cannot get this even now, AFT is the alternative and is perhaps better. Make sure you get ATF which is supported by the 722.6 transmission. ATF is red in color and the old Benz oil was green/yellow. You will need additionally a new filter, a new oil pan gasket, new drain plugs and copper washers, new electrical plug and gaskets. So it adds up!

Meyle Transmission filter kit
Meyle Transmission filter kit. Comes in a neat box!

Therefore I recommend to get a transmission fluid kit which contains all these things. Meyle has one great such kit, which is not too expensive either. I highly recommend it! https://www.meyle.com/en/passenger-cars/drive-components/oil-change-kits/ It cointains 7L of ATF, filter, drain plugs and washers, gaskets, connector plug, a drain pan magnet, fluid cap tab, drain pan bolts.

Meyle transmission filter kit
Filter kit from Meyle. 7L of fluid, filter, gaskets, bolts and much more!

Also since Mercedes Made this as “sealed for life”, there is no dipstick. And the dipstick tube is sealed with a red tab. This tab you need to break off in order to remove the dipstick tube cap. These can be bought as replacement or it comes in the transmission fluid kit. You will need also a dipstick to be certain of the fluid level after refilling. Get an disptick on Ebay, there are loads of options, but make sure it is long enough. It has to be at least 1200mm long for the 722.6 if you have the M120 engine. Aftermarket versions are totally fine here, do not throw your money away on a Mercedes one when you can get literally the same function for a fraction of the price.

Aftermarket dipstick on Ebay
Aftermarket dipstick from Ebay. 1200mm long.

You can try to skip the whole dipstick tube and just fill in the amount you drained, but it should only be done if you are 100% certain that the level is correct. Usually these transmissions tend to have leaked a bit over time through old gaskets after 20+ years.

Tools needed:

  • Dipstick 1200mm at aleast
  • Hex socket
  • Torx socket
  • Torque wrench with low scale (5-25Nm)
  • Drain pan
  • Small funnel
  • Rags/lint free paper
  • Brake cleaner

Procedure

Changing the transmission oil for the 722.6 is a multi-step procedure and is a bit more advanced than changing the motor oil. The procedure is divided into a few sections below.

Warming up the transmission

Start with warming up the transmission to operating temperature, this is done by driving it before you start the job. So make sure you prepare everything before so you can jump straight into the job. 5-10 minutes driving at high speeds will be enough. Then with the car running and on a flat surface and standing still, go through all the gear levels with the gear shifter 3-5 times leaving the stick in each level a few seconds. Then put it in park still with the engine running, open the hood and pry off the red plastic tab on the dipstick to open it.

disptick level measured
Dipstcik level measure, level here was a bit low. And notice the green and filthy oil on the paper

Now measure the fluid level with the dipstick. The way to read the dipstick is dependant on the dipstick itself, however there are two levels, one for cold and one for warm transmissions. Use the upper warm level and see how much oil is left in the transmission. Mine was quite low, certainly above the cold level but lower than the minimum warm level. Measuring before can make an indication on how much oil you need to add and if it has leaked any oil.

The main reason for warming up the transmission before the oil change is for the oil to drain much easier, since it has to pass through the labyrinth in the valve gallery. Now raise the front of your, either with jack stands, or drive it up onto ramps. Shut off the car and put it in Neutral.

Draining the old fluid

Have a clean drip pan available. Keep it clean so you can spot debris or transmission material in the old oil after you have drained. This will tell you about the condition of your transmission. Have the drip pan completely empty so you can later measure the drained quantity. This will make it much easier know how much oil you must add later.

Clean drip pan
Clean drip pan ready for draining oil

Place the drain pan under the transmission oil pan. Use a hex socket to open the drain plug. Here you might have issues actually loosening the drain plug, if it has never been opened before. This bolt can seize incredibly hard. Mine got rounded off completely and I needed a bolt extractor tool to get it out. Thankfully a new plug comes with the transmission oil change kit.

Transmsission oil pan bolt
Transmission oil pan bolt

Be ready for the oil to drain out with immense speed. Be careful not to burn your hands on the warm oil. Already now you can see if the oil has been changed before and within reasonable time. My oil was very black and brown and for sure never changed since the car was new. The evidence for that will come later below.

Draining transmission oil
Draining transmission oil. Notice the black-brown colour. Yuck!

The oil will drain for quite a long time so take a 20 minutes coffee break. When you come back the oil should only slightly drip out. Reinsert the plug so the dripping will stop for now.

Note on draining the Torque converter

Now is supposed to be the time to drain the torque converter, but since I forgot to do it, that part is left out here. I will update this article in the future with draining the torque converter, perhaps in coming spring/summer, since I need to do another transmission oil to completely remove out the old oil. Anyway the torque convert bolt should be accessible at the front end of the transmission through a small hole. To access it you need to turn the engine over by hand. Therefore it was important to put the gear in Neutral. The engine can be turned over by hand by inserting a socket into the crank pulley and rotating it clockwise. Do this until the torque convert bolt is shown. Alternatively you can turn just the torque converter by using a large screw driver or pry-bar which you carefully push on the torque converter itself. This must be done also in a clockwise direction as seen from the front of the engine. The bolt is loosened with a 5mm hex. Torque here is 10 Nm.

Removing oil pan

Transmission drain pan bolts
Transmission drain pan Torx bolts

Now it is time to remove the transmission oil pan. This can be a bit messy, so do not wear your nicest clothes. It is held in place with six Torx bolts. You also have to remove the bolt securing the wire on the right front corner. Undo all of the bolts then leave a couple in the corners. Now use one hand to support the pan while you undo the last two bolts and gently lower the pan to the floor. The pan will contain a lot of transmission fluid trust me.

Cable fastener transmission
Remove the cable fastener bolt in order to remove transmission pan bracket.

With the transmission pan on the ground, you can now inspect it for particles, shavings etc in the remaining oil. This really shows the health of the transmission. My pan looked alright, but there was noticeable sludge at the bottom. There were no magnet either. Probably the factory oil. The next clue in the next section.

Transmission pan with oil
Bottom of the transmission pan. Oil is old and very filthy. Some sludge is present. Notice the lack of a magnet.

Replacing oil filter

Now it is time to replace the oil filter. Just pull the old one off straight down and notice the orientation, there is a plastic tab which goes into a slot. The old oil filter might have a date on it. My old filter was from 1995, meaning it never have been changed since the car was sold new in 1996. So this explains the gunky oil and harsher shifting of the transmission after 100.000 km and 25 years. Unbelievable that it never was changed earlier, probably due to the low mileage.

old transmission filter
Old transmission filter from September 1995. Archaeology at its best. This goes straight into the storage at the museum.

The little plastic tab on the filter goes in the slot shown below.

Location of oil filter slot
Location of oil filter tab slot.

It is advised not to touch the valve body too much to get dirt on it, but you can inspect it and wipe it off slightly with a lint free cloth. However the transmission will continue to leak so maybe just leave it alone. If you need to change the conductor plate, then the whole valve body needs to be removed. Utter cleanliness needs to be followed.

Transmission valve body
The transmission valve body. This has to be take noff if the conductor plate needs to be removed.

Now take the new oil filter and place it under the valve body, make sure the tab aligns in the slot and simply push the oil filter into the hole. The filter will not sit super tight and might feel a bit wobbly, this is normal, but make sure it is pushed all the way in.

Transmission oil filter fitted
New transmission oil filter fitted to the valve body.

Replacing transmission connector housing and gaskets

Next step is to replace the connector sealant inlet, which is located just above the valve body on the right corner of the transmission. The oil change kit comes with a new connector inlet body and new gaskets. The old ones tend to get leaky due to old gaskets and the plastic brittle due to years of experiencing heat.

Transmission connector location
Transmission connector location

The way you loosen the connector, is to flip the tab on the outer plastic ring downwards. This will free the connector which will make access to the connector plug. Just pull out on the cable and the cable should come loose.

transmission connector tab
Flip down transmission connector tab as shown

Study the new connector housing and you see there is a little bolt in the middle of it. The old connector plug housing has to come out by loosening this bolt. Use a long 7mm socket and a flexible extension in order to get it out. It should not sit very tight.

New transmission connector housing
New transmission connector housing. Notice the little bolt down in there
7mm socket to transmission cable housing
Use a 7mm socket to loosen the bolt for the transmission cable housing
taking out the transmission connector housing
Use a flexible extension to get the connector housing out. The angle of attack is a bit tricky without.

With the bolt loosened you can just pull out the connector housing. It might be a bit stuck if the old gaskets are gripping, but just pull and it should come out. Inspect the connector pins and clean up any dirt and oil in the connector hole before replacing the new housing.

new vs old transmission connector housing
New vs old transmission connector housing. Notice the placement of the two gaskets.
Transmission connector pins
Transmission connector pins

Study the orientation of the connector pins so you will be able to get the connector housing in the right orientation. Pop the new connector housing in and make absolutely sure you are lined up before pushing it in. Bending connector pins will be a lengthy procedure where you will need to replace the conduction plate. Tighten the bolt just enough to be snug, do not overtighten here otherwise you will break the plastic.

new connector housing
Place new connector housing and tighten bolt

Now just plug plug in the transmission wire and tighten the cable with pushing the connector tab upwards.

New connector housing in place
New connector housing in place, without further leaks

Replacing oil pan gasket

Clean the transmission oil pan thoroughly and throw away the old gasket.

transmission oil pan dirty
Clean up old sludge in transmssion oil pan
New vs old transmission gaskets
Old vs new transmission gaskets

Place the new gasket over the cleaned transmission and remember to put in the new magnet if your transmission oil pan did not have one already. If the old one is cracked or have shavings in it, just replace it. Also remember to replace the old drain plug and copper washer.

Cleaned transmission oil pan
Transmission oil pan cleaned. Leave no trace of dirt whatsoever in it. Notice the placement of the magnet. The magnet will preserve the transmission longer and will allow you to spot metal shavings during the next oil change.

The transmission oil change kit comes with new transmission oil pan bolts. Preferably use these. There are 6 torx bolts to secure the pan. Along with aluminium spacers which you should now clean. Also clean the entire surface where the gasket will sit on the transmission to ensure a proper seal.

New bolts for oil pan
New bolts for oil pan
Remember to secure the cable in the front right corner

Hand tighten all bolts before torquing them down. Use a small low scale torque wrench which you know is good. The drain plug is torqued to 14 Nm and the pan bolts are only torqued to 8 Nm. Go around them a few times, since tightening adjacent bolt will loosen the one next to it.

Torque oil pan bolts
Torque oil pan bolts to 8 Nm. Drain plug is torqued to 14 Nm.

Adding new transmission fluid

First see how much fluid you have drained, pour the old oil into one used oil container or similar so you can measure the level. This is especially important when you have not drained the torque converter, since you will not get all the oil out. To be precise, you will never get all of the oil out. And fluid level is more important than with engine oil. Keep in mind that you might add more id the fluid was a bit low before you drained the transmission. As was the case with mine.

Drained fluid quantity check
Checking the quantity of the drained fluid

When you know how much quantity you can add. Start by pouring the required quantity into the dip stick hole, use a small funnel to avoid spills, also pour slowly since it will use some time to get down the long dipstick tube. Avoid spilling since it it will not be good for your manifolds to get oil on them.

Transmission oil refill
Use a small funnel in the dipstick hole before pouring.
Pouring in new transmission fluid
Pouring in new transmission fluid slowly to avoid spills.

In order to check the level the engine must be running. Remember to put the dipstick lid back on, but do not place the locking tab just yet. Let the fluid run down into the tube for a few minutes before doing anything else.

Warm up, test drive, fluid level check and inspecting for leaks

Before going for a drive. Lower the car back to level. Then start the engine and start cycling the transmission through the gears with the leaver slowly. Do this 3-5 times with the lever in the different gears a few seconds. Then with the car still running, place it in park. The transmission is now still cold, but initial measurement must be done before driving off.

Cycling gears for transmission oil check
Cycling gears for transmission oil check

To measure the cold level, you will need to insert and reinsert and clean off the dipstick a few times before you can get an accurate reading. Note that the level should be not higher than the cold mark. Also note that measurement while the transmission is cold is more inaccurate than when warm. If the level is way over the cold mark, you must suck up some fluid since it is overfilled. IF OK, then check under the car that no transmission is leaking out. Take with some extra transmission fluid, the funnel and rags. Then go for a spin.

When you have been driving with highway speeds (>80km/h) for about 10 minutes, find a gas station or similar with a level surface. Do not turn off the engine and cycle through the gears again with the lever. Set the gear in Park. Then measure with the dipstick, wipe it clean reinsert and measure until you get a clear reading. If the oil level is now below warm marking, pour in only 100 ml at a time before measuring again. Cycling through the gears is necessary between each re-measurement and always keep the engine on . Repeat the process until the level is in between minimum and maximum at the warm level on the dipstick.

Finally you can install the little red tab so it can secure the dipstick tube cap.

Cheers! Robs out!

How to Change Differential Oil in W140 S-Class

Apart from power steering fluid, this has to be the most neglected fluid change on a car. The intervals are usually long, sometimes in excess of 60.000km, but if you have no history on when this was last changed it is probably a good idea of changing it. It might give you a smoother ride with less rear end noise. At least it gives peace of mind and the job is fairly simple.

Preparation

You will need to get some differential oil from the store. 1.4L to be exact, but in practice that means two bottles of fluid. The differential can either take 75W-90 or 85W-90, you have to decide what is best for you. It should be API GL5 quality at least. I chose to put in 85W-90 since I had good experience with that before. Some bottle comes with a little tube which you can use to fill the oil with. This oil is very thick and is a bit tricky to squeeze into the differential. Consider getting an oil pump which will make this job much easier and faster.

As for special tools you will need a 14mm Hex Socket for the drain plugs.

14mm hex socket
14mm hex socket for the drain plug

Also prepare some brake cleaner and rags to clean up underneath the diff while you are there.

Procedure

Make sure the differential oil is fairly warm, if it is summer it will drain ok without driving it first, but if it is a bit cold outside take it for a short spin before draining the oil. The oil will drain out much easier when it is warm.

Start by raising the entire rear end of the car up. Make sure to block the front wheels from rolling since there is no parking brake there. Secure the rear with jack stands so it is safe to work under. It is possible to put the jack stands int he area behind the rear axle, so you can use the jack normally to raise the car.

Raise rear end of car
Raise rear end of car

Inspect for leaks on the differential, they usually are a bit dirty. I hardly ever see a leak free differential, and they seem to seep no matter what, often they stop seeping by themselves too. No hurry in changing seals unless you see a puddle under the car when it is parked for a few days. Yours is probably looking something like in the picture below. Here the oil was very caked on and old, not fresh as far as I could see.

Dirty differential
Dirty differential, clean with brake cleaner and paper/rags
Differential cleaned
Differential cleaned

After the differential is fairly clean. Locate the upper drain plug on the differential. It should be on the left side just in front of the axle. Be sure to loosen this top drain plug first. This trick is to ensure that you can stop the job and still keep driving if you are unable to get the upper or lower drain plug open. If fluid runs out from the top drain plug, the level is topped off. If not, feel it with a finger to estimate how much oil is missing.

Upper differential oil plug
Upper differential oil plug. Located on the left side in front of the axle

When the upper drain plug is loosened. Now it is time to drain the fluid, open the lower plug and keep clear from the flow into the drain pan. Try to hold on to the nut so you do not have to fish for it in stinky oil afterwards. Differential oil is very stinky stuff, and more so when old.

Open drain plug
Open drain plug to let old oil out
Draining differential oil
Stinky and filthy differential oil pouring out

The oil from my car was absolutely stinky and very filthy, it had turn into a totally brown goo. The oil level was not completely full either it seemed. I think the differential oil here was never changed in the car’s lifetime. Good thing I got to it before differential wear started happening. Now it is a good time to check this oil in the drain pan if it has any metal shavings in it. Also stick your finger into the drain hole and see if you can feel any shavings inside. You can also stick in a magnet and check if you find any. Luckily my car had zero metal shavings which I could find.

Inspecting oil pan for metal shavings
Inspecting oil pan for metal shavings. Here there were none

Remember to put back the lower drain plug. No need to torque it, but it should be torqued to snug with a normal sized ratchet, do not over tighten this. Clean the area around so you can spot leaks after.

Now get your fresh oil and squeeze it into the upper drain plug. Either the bottle you bought have a filler tube, or you have a large syringe or a gear oil pump. I use Mobil1 85W-90, but you can choose of course whatever the brand you like, I do not honestly care.

differential oil bottles
Mobil1 85W-90 API GL5

After you have refilled the oil and lowered the car back to the ground. Take it out for a short spin, come back and look under the differential for leaks. Hopefully the ride will be a bit smoother!

Cheers, Robs out!

Changing CV-axles on W245 B180 CDI

Including Ball joints and Tie rods

Having weird clunking sounds while driving or the steering wheels starts to shake when you are driving and getting worse with increased speed? Also the tires get worn excessive at one of the sides? This could be a sign that the CV axles going bad. It is possible to change out just the CV axle ends and not the whole axles, however it is more time consuming and often easier just replacing new complete axles. Changing the entire axles will only be covered in this article. The job can be pretty extensive and complex if you have not much experience in working on cars due to the requirement of time and many tools needed. Although it can be straight forward if you have some knowledge of mechanics. If your car have driven in a rust environment and you don’t have special tools, then maybe skip this job!

This will be a long one so fasten your harness and prepare a big tea pot!

Preparations

There are some considerations to be done. The original axles will probably fit the car better than after market ones. I find a lot of complaining around forums for poorly fitting after market CV axles for front wheel driven cars. Some cheap brands in reality sometimes use refurbished old axles and pack them with little grease and they might end up making sounds and break after a short time. Therefore be sure not to throw out your original MB axles without really being sure about changing them. Getting new MB axles for the B-class I would not recommend since they are crazy expensive and not offering any benefits other than being original. A good middle way could then be to buy a CV joint end refurbish kit. However this procedure is not covered here.

I wouldn’t buy the cheapest, but not the most expensive you can find either. Choose a brand you trust in the middle range. That will be 95% as good as the best ones. Also make sure the lengths and fitting are correct before ordering, parts stores list all kinds of variations, and manual and Auto/CVT variations are different even if they look similar in images.

There is a high chance you need to change the axle seals from the transmission while changing the axles. This could be because of age or they get damaged when removing/installing the axles. I didn’t think of this and one side started leaking a lot and I needed to take out the axle again. The axle seal for the CVT version I could not find in any online store, and needed to order one from Mercedes dealer and prised as such too!

You can be sure to need changing the lower ball joints and tie rods unless they have been changed in the last few years. This will add the need for a wheel alignment after the job. This needs to be done at a workshop unless you have really advanced equipment and training. A wheel alignment is quite cheap though compared to the changing of the drive shafts, so I would still consider changing the CV axles DIY.

There is a chance you will need to refill some transmission oil if some leaks out during installation. This is a good opportunity to change the filter and gear oil. This however requires you to have a dipstick and more parts on hand. Mercedes does not want their customers to change their oil, so they “sealed” the cap off and there is no dipstick. You can get a disptick for 5 bucks at Ebay, good filter kits also include the little plastic tab. Changing transmission fluid will not ne covered in this article.

You will need some special equipment for this

  • E-Torx bits (for removing bracket to right side axle and the ball joint bolts might have them)
  • Large star socket (for the original axle end bolts)
  • Glide hammer (to remove axle shaft seal)
  • Torque wrench
  • A good selection of spanners
  • Large and powerful tie rod and ball joint remover
  • Large sockets or similar to fit over the axle seal lip
  • Various lengths of socket extensions
  • Large soft ended hammer
  • Hex wrenches
  • Thread lock
E-Torx E14
E-Torx E14

You will need the following parts, depending on ambition level

  • Left side CV axle, is shorter than the other
  • Right side CV axle, is longer than the other
  • 2x Axle seal/ transmission output seal
  • 2x Ball joint
  • 2x Tie rod
  • CV moly grease
  • Ball bearing grease/assembly grease
  • High temp anti-seize alu-paste
  • 1L Transmission fluid – type depending on your transmission
  • Optional: Dipstick /Auto Filter/gasket

If you decide to go through with this job, be prepared that the tie rod might have rusted completely to the hub/knuckle. Then you will need large amounts of patience, cutting and drilling to get it free. I really hated this part. You are hereby warned.

Plan for not driving the car in a few days. This might take you longer than you expect. If you see an obstacle you cannot fix and you need the car, then quit early before the point of no return. I had not planned it very well and lacked both tools and parts thought the whole process. So the car was jacked up on stands while I waited on new parts to arrive. I guess this is how you learn. Luckily I had a backup car so there was no stress. Although I didn’t plan that the car could not be driven for over 2 months straight…

Procedure

Before you raise the car, you will need to loosen the huge axle spindle nut. Take off the middle cap from the rim. If there is a dust cover hiding the spindle nut, then just raise the wheel with a jack and take the wheel off. Then remove the dust cover for the wheel hub, put the wheel back on and lower it to the ground again. Then loosen the spindle nut, use a long breaker bar because this one sits really tight!

Wheel hub dust cap
Remove wheel hub dust cap
Axle spindle nut
Axle spindle nut. The original is this star shaped. New after market CV axles comes with normal socket nuts to replace these.
Loosening axle spindle nut
Loosening axle spindle nut. They sit on tight so use a long breaker bar.

Do this for the other wheel if you plan to change both CV axles. After you removed the spindle nuts, you will need to raise the entire front of the car so you can get access underneath, so put it on safe on jack stands.

Next is two different ways to loosening the tie rod. The easy way if it’s not stuck. And the hard way if it’s stuck.

The easy way

Since this is the easy way, you don’t even have to take the caliper or brake disc off! Super easy right? If working on the right side, turn the wheel completely over to the right to get better access. Opposite for the left side obviously. Spray the tie rod bolts and the lower ball joint with penetrating fluid and let it work a few minutes before continuing.

Start by loosening the 19mm tie-rod nut on the hub knuckle assembly with a socket. The tie rod will stick to the knuckle arm because of the press fit, so the bolt will loosen by itself. Now you will need the heavy duty tie rod/ball joint puller tool. Place it over the tie rod and pop it.

Loosening tie rod bolt
Loosening tie rod bolt
Tie-rod puller
Snap off the tie rod with the ball joint tool.

Hopefully it will snap off and it will look like below:

loosened tie-rod
Tie-rod loosened

Now move over to loosening the lower ball joint. Since this is the easy method, you can avoid loosening the ball joint completely from the the lower suspension arm, unless you want to change the lower ball joint which I highly recommend. Use a 22mm spanner, you are not able to fit a socket over it. This bolt can be very tight so you might use a bit of muscle. You will normally not need a hex to stop it from turning when loosening since it is press fitted after tightening. The image below is in fact from tightening, but shows the same.

Lower ball joint
Loosen the Lower ball joint with a 22mm spanner. The hex is only needed when tightening. It is press fitted.

Hopefully it will look something like this when loosened:

Loosened ball joint nut
Loosened ball joint nut

Now get the ball joint puller tool again and snap off the ball joint from the steering knuckle. I don’t have a picture of it here, but you should figure it out since you did the exact same procedure on the tie-rod like 5mins ago.

After it is snapped loose, get a long pry bar, place it in the inner hole of the lower suspension arm and press down as far as you can with the bar leverage. This will enable you to lift the steering knuckle out of the ball joint.

Ball joint w245
Free ball joint of the steering knuckle. It is possible to free the CV axle spindle from the hub.

Withe knuckle free from the ball joint you can now easily free the CV axle spindle from the hub. You can normally drive it out with not too much effort.

The right side CV-Axle

The right side is slightly more complicated to remove, since it is longer and has another bracket under the car. Locate the bracket, it is secured with two Torx bolts.

Right side CV axles
Right side CV Axle. Contains a bracket in the middle.
Bracket for right side CV axle
Bracket and torx bolts

Now you can go ahead of pulling the CV axle out of the transmission. It might take a bit of force. On this side there is no place you can pry off the axle either. Be sure to have a drip pan under the transmission in case fluid runs out.

Right CV axle input into transmission housing
Right CV axle input into transmission housing
After CV axle is removed.
Bracket After CV axle is removed.
Right side CV Axle removed
Right side CV Axle removed

Left Side:

The left side is a bit easier, it can be pulled out straight away after the tie rod end and the ball joint have been loosened. It’s nearly impossible to pull the drive shaft straight out, due to the locking spring on the inside. Get a pry bar with the flat end and fit it between the inner edge of the drive shaft and the transmission housing. This will loosen the drive shaft from the transmission. Be ready for a drip pan if transmission fluid leaks out.

Prybar slot drive shaft
Prybar slot for left side drive shaft
Left side drive shaft loosened
Left side drive shaft loosened

The Hard Way

Let us imagine that the tie-rod is completely stuck and you cannot remove it with a tie-rod tool, either it breaks or it will not budge. Then what? Let me show you the hard way to fix this. In order to do this, you will need a set with good quality and new sharp drill bits. Also you will need to use an angle grinder. Rub on that patience lube you have in the bottom of your tool kit since you will need it! Let me show you how below.

Unbolting tie-rod
First step so easy. Unbolting the tie-rod.

First you will try to undo the tie-rod like normally, then your tool breaks or bends or worse. So your mind realise it is not budging at all. Fuck! You might be tempted to use a large sledge hammer to knock it free. Do not under any circumstance try this because you might end up bending the knuckle hub assembly. Do not bother to use a blow torch with heat either, it will not work and you will just end up burning the ABS sensor. The tie-rod sleeve will definitively burn up, but it will get ruined now anyway when it is this stuck.

Forcing the tie-rod tool
Forcing the tie-rod tool until it breaks. Failure!

To get better access you will need to remove the brake disk. Unbolt the caliper and hang it up with some wires to reduce the stress on the brake hose. Now bend the brake dust slightly shield out of the way, or unless it is rusted like mine, just tear it off.

Cut tie rod stud off
Cut tie rod stud off to prepare drilling. In the image you can see the tie-rod sleeve is burnt, so yeah I tried heat with no success. Do not bother with heat. Just start drilling.

Now the long and tedious process start. It is not without risk. If you do not take care you will need to replace the entire knuckle hub assembly. It will need to be replaced if there are scores inside the tie-rod insert after you drill it out.

Start by drilling with a small sized drill to make a pilot hole. Make absolutely sure that is in the middle other wise you will get out of the center line and might end up scoring the hole. You are hereby warned. The more narrow the drill the easier it is to get it started in the beginning. Use low speed and stop to apply oil to the drill bit head often in order to cool the drill bit head. Otherwise you will need to replace the drill often. This metal is super hard and will take a lot of time to get through. If you take it slow and use oil often it will not wear out your drills. Drill at least one centimetre before increasing the drill size. I used between 2-3 hours to get through the tie-rod before it popped out.

Drilling tie-rod
Drilling the tie-rod with narrow drill bit at the beginning. Go very slow and apply plenty of oil to aid in cooling the drill bit.

After you increase the drill bit size, make sure you don not score the knuckle hole. Go very slow and swap between the narrow and thick drill bits after you have gone a bit deeper.

Increase drill bit size
Increase drill bit size after you have a decent size hole. you will need to swap between them as you go along.

When you have traversed the entire length of the knuckle arm, about 2 centimetres, do not increase the drill bit further. Now grab your trustworthy punch drive which can fit in the tie-rod hole which you have drilled. Use some force and I’m sure will pop out. Try a few different sizes and continue drilling if it will not pop out.

Tie-rod drilled out
Tie-rod drilled out. This is the leftover which only let go after removing over 90%. Very stubborn indeed.

The ball-joint for some reason is not usually this stuck and can normally be removed by the ball joint remover tool. If this is completely stuck as well, then you might require help from a workshop, since it is very much harder to access. Have no solution for you here.

Changing drive shaft-transmission seals

I highly recommend to do this step since it is a high chance it never was changed prior and might start leaking. It is also easy to damage it when taking out and inserting the new drive shafts. I learned the hard way, it started leaking and the car probably lost 05.-1L of transmission fluid. And I had to take out the left side CV shaft out again. I did not change them initially since I got the wrong seals from the place where I ordered the rest of the parts. They did not have the right ones, especially for the CVT transmission variant I think they are hard to find? Anyway I needed to get them from a Mercedes dealer. And the price was 60$ each… OMG that is excessive! Anyway this is how to change them.

Removed drive shaft seal
Removed drive shaft seal

You will need a slide hammer puller to get them out since they will sit incredibly hard in the transmission housing. Put the new ones in your freezer since the outer diameter will shrink slightly and it will be much easier to insert into the housing. Timing here is essential. Get the old ones out before you ready the new ones. If there are any scores or rust marks in the inner edge of the transmission housing, you will need to use a bit of fine sand paper and polish the surface clean. I promise you it will leak if you skip this step. You will only have one shot of getting the new ones in. If they go in crooked and you bend them, you will need to get new ones. Therefore it might be smart to practice getting in the old ones back in first if you never did this kind of job.

Installing requires an equal size socket tool which matches the outer diameter of the seal. Get your favourite grease ready to easy the inserting of the seal. I used ball bearing/ hub grease. Use a long socket extension which you can pound on. Now when everything is ready, run and get the new seal out of the fridge and be as fast as possible, every second here counts! Grease up the new seal while it still freezing and install.

Grease up the new seal
Grease up the new seal while it is still freezing cold.

Use the socket and tap it in with a rubber hammer. Make sure to tap it in carefully and checking often that it goes in straight. When the outer edge of the seal is parallel to the outer edge if the transmission housing it is in the right place. If you overshoot, then you have to pull it out again. There is no end edge in the housing which tells you when it is in. So it is very easy to drive it too far in. The inner dust flap of the seal will stick out from the edge and will fit inside the drive shaft dust cover.

Tap in the seal
Tap in the seal
New seal in place
New seal in place. Notice the outer edge is parallel to the transmission housing.

Now you should be ready to put in the new drive shaft.

Fitting the CV drive shafts

Try not to pull the CV shafts apart since you might end up in a situation where the balls inside the joints will fall out of their sleeve and the joint will not function properly. First lets do the right side.

Fitting the Right side

Firstly put some grease on the drive shaft end that goes into the transmission. This will aid the locking ring to slide into place.

Grease drive shaft end
Grease drive shaft end

Use a rubber hammer and knock in the drive shaft into the transmission, make sure it is all the way in. The shaft should now line up with the intermediate bearing bracket holes. Use some thread locker on the bolts and tighten to reasonably tight.

Frive sahft intermidiate right side bracket
The right side drive shaft intermediate bracket should line up. Use thread locker on the bolts and tighten

Fitting the left side

Fitting the left side is just as fitting the right one, except the intermediate bracket fastening. Be sure that the drive shaft is far enough in so the dust cap goes over the inner seal rubber flap.

Fitting the end

If you need to change the lower ball-joint and the tie-rod, this is how you do it.

Remove the lower ball joint. Here you will need the E-torx if it is the original one still attached.

3 E-torx bolts securing the lower ball-joint with the suspension arm
3 E-torx bolts securing the lower ball-joint with the suspension arm

Once it is off, use a round wire brush to polish the inside the ball joint hole and the tie-rod insert hole. This is to remove any rust or left over dirt. This is a very important step in order to make them fit snugly.

Polish the lower ball joint hole
Brush the lower ball joint hole

Then use the same brush to clean the tie-rod hole.

Brush the tie-rod hole
Brush the tie-rod hole

Remember the tie-rod that might get stuck. Now use some anti seize Alu-paste to lubricate the lower ball joint and tie-rod holes before fitting them. So the same situation will not happen again if you need to loosen these again. Prepare for the worst you know.

Alu paste in tie-rod holes
Anti seize Alu paste in tie-rod holes

Ready now the new parts for fitting.

New parts vs old
New parts vs old. The older are a bit crusty. The left side is the cut one which was stuck and cut, needed a change here.

The new ball joints will usually have normal bolts instead of the E-torx ones, except the ones I ordered didn’t come with new bolts so I had to reuse them. This is totally fine. The top bolt always are new, do not reuse these, since they have a locking plastic ring. So here you don not have to use thread locker. Since you have to use a spanner to tighten the ball joint bolt, you can not use a torque wrench normally, so tighten with some force within reason. It will be pressed in the fitting and will not come loose.

New lower ball joint fitted
New lower ball joint fitted.

Before you insert the CV shaft into the hub, you will need to polish the inner hub surfaces. It is probably a bit rusty. Clean it up with sand paper so it is completely smooth.

Rusty inner surface of hub
Rusty inner surface of hub. This needs to cleaned with sand paper.

Use some CV lithium-moly grease for the interface between the CV shaft and the hub. This is important to keep noises and vibrations from the hub after you fit a new CV shaft. This is a common problem on front wheeled drive cars, the knocking after you replace completely new axles. Especially on Volkswagen and Audis. M ake sure to follow their recommendation with using CV moly grease.

CV Lithium moly-grease
CV Lithium moly-grease
Grease the inside of the hub
Grease the inside of the hub with CV moly grease
Grease the inside of the CV shaft where it interfaces with the hub
Grease the inside of the CV shaft where it interfaces with the hub

You do not have to grease the spline where it goes into the hub. Since you want to avoid slipping change of the drive gears.

Lower ball joint
Loosen the Lower ball joint with a 22mm spanner. Use a hex. wrench to hold the stud from rotating.

Now mark the spot where the tie-rod was and unscrew it from the steering rack rods. Put the new ones in in the exact same length as the ones you put out. You probably still need a front alignment job after this, but might at least make the car go somewhat straight meanwhile. Put some anti seize alu-paste on it.

Steering rack rod
Steering rack rod. Put some anti seize alu-paste on it!

After tightening then put on the tie-rod end on the hub knuckle assembly. Use at first a spanner and the hex to keep it from spinning, then tighten snugly. Then move over to the torque tool and tighten it to 60Nm.

Tightening tie-rod
Tightening tie-rod. Tighten to 60Nm.

If you removed the brake caliper, these bolts needs thread locker and then tightening to 115Nm. The little bolt to the brake disk which goes on the hub needs thread locker and only 15Nm.

After tightening the tie-rod, the only remaining is to tighten the CV drive shaft spline nut. To to this, the wheel have to go on first. And then lower the wheel to the ground so you can tighten the nut. The torque tool has to be set to 100Nm and then then tighten 60 degrees more after your each the torque setting. Prepare marks on a circle so you know roughly how much to torque. There is even apps on your phone to to this, or make circle from paper and put it on yourtool. Or buy a tool which tells you exactly the degrees.

Tightening the CV drive shaft nut
Tightening the CV drive shaft nut. 100Nm then 60 degrees.

After torquing the drive shaft spline nut, raise the wheel up. Take off the wheel. Put the hub dust cap back on then put the wheel back on.

If any transmission fluid came out it the time to replace this with the exact amount which came out. This might not be needed, depends only if some transmission fluid ran out during the job.

Take the car for a test drive and listen and feel if there are any weird sounds or vibrations. If all good you are done. Consider you a master of mechanics DIY jobs. This job is not easy and you should be very proud!

Robs Out!

How to change automatic transmission oil and filter in W123

Now to the post you all have been waiting for. Time to defy old myths and the car companies themselves! Mercedes usually warns about changing the transmission oil yourself and in newer models they are so called sealed where you cannot even measure the fluid level without buying an accessory dipstick. I do not agree on this level of manufacturer control and you can totally do this yourself even on a Mercedes. Sometimes I really think that car companies have a bad attitude towards their customers. Just take for example the VW diesel scandal which they tried to cheat everyone…

Thoughts

Fluid changes are the number one maintenance priority of making your car perform optimally and mitigating excessive wear and damage. Fluid changes of the transmission oil should always be your concern. Some idiot say that changing automatic transmission oil in an old car will cause it to slip and thus you should not change oil. This is only true if the transmission is already very worn/broken and the only thing keeping the transmission from slipping is the high friction of metal particles and the old smudgy oil which is totally broken down and provides little friction and cooling. Then of course it might starting slipping when fresh oil is added which sole purpose is to give less friction and cool the internals. However not changing the oil will only delay the inevitable of total transmission failure.

A good transmission will always benefit from an oil change since this reduces friction and wear!

Mercedes does not recommend this job and it should be left to the “professionals”, all my respect to the mechanics, but they work on a hectic schedule and the quality of the oil change might not be perfect 100% of the time. Not saying they usually make mistakes, because they usually don’t when talking about good workshops. Anyway I think changing automatic transmission fluid is something you can easily do yourself on a Mercedes as any other car. It is not as easy as changing the engine oil, but not very difficult either. There are some fall pits so just be prepared IN ADVANCE.

I cover here the procedure for the M110 engine with the 722.xxx transmission. The procedure is basically the same for all older Mercs. Changing the automatic oil will give you a good indication about the condition of your transmission unit so you can take preventative measures or just continue like usual.

Preparation

You will need to get some new stuff

  • 6.6L ATF Dex3 on earlier models
  • 6.1L ATF Dex3 on later models (usually 81-85)
  • New filter and oil pan seal (get the right one from Mercedes)
  • Narrow Funnel
  • Brake cleaner
  • Shop towels (lint free)
  • Jack stands and jack
  • Dripping pan
  • Tools – sockets and hex bit
  • Torque wrench
Draining

Unless it is a very warm summer day, go for a drive (recommended is 24km to really warm up the transmission to operating temperature, but sure you can go less if it’s highway speeds) , it will drain easier and faster when warm. Try planning to do this work when coming back from work or after a trip to the store to avoid unnecessary driving.

There are two choices when draining the fluid. Either just from the oil pan or both from the oil pan and the torque converter. I highly recommend to drain from both so you can get rid of as much of the old oil as possible.

Torque converter mercedes 280ce
Torque converter, but no drain plug in sight. The engine has to be turned.

Get the car up on jack stands, at least in the front. Block the wheels and apply the parking brake. Put the Transmission in Neutral (N). Start by locating the torque converter at the front of the transmission. In 99% of the cases you will have to turn the engine so the torque converter drain plug is pointing straight down so you can access it. In order to turn the torque converter you will have to have the car in Neutral! Use a socket wrench to turn the crankshaft pulley bolt in front of the engine and rotate the engine CLOCKWISE. If you have a helper he or she can tell you when the torque converter drain plug is coming into sight. Otherwise you have to crank the engine a bit at a time.

Torque converter drain plug mercedes 280ce
Torque converter drain plug in position for draining.

When you turned the engine so you can see the drain plug, don’t drain the torque converter before you have started draining the oil pan.

Open the oil pan drain plug with a hex socket, be careful to avoid burning yourself on the warm oil suddenly coming out very fast! Do the last unscrewing by hand to catch the bolt so it doesn’t fall into the drain pan.

automatic transmission oil
Draining the transmission oil pan

When no more oil is coming out reinstall the drain plug so you won’t loose it. Now you can remove the torque converter bolt with the same procedure as with the pan. Reinstall when no oil is coming out of the torque converter.

Now it is time to remove the oil pan completely for installing the new filter. The pan is secured with 6 bolts. be careful to hold it horizontally when loosing the last bolts because the pan contains a lot of oil still. After the pan is removed, let the fluid drip for a while from the valve body before removing the filter. Cleanliness at this point is of importance, do not wipe off the oil coming out of the valve body or you might get dirt on the valve body which is quite bad. It is pretty hard to clean the valve body since oil is constantly coming slowly out of it underneath for days.

The filter is held by three Phillips screws, be careful to not loose these screws! Also be careful of even more fluid coming fast at you when removing the filter from the valve body.

With the filter gone, the transmission will keep on dripping slowly, I mean for days if left like this. So have the drain pan under at all times.

The quantity in the drain pain will determine how much oil you need to add later. Overfilling the automatic transmission is not good due to overpressure which may lead to excessive fluid leaks and foaming of the oil.

Inspection

Now it is time to inspect the oil pan for metal particles, and fluid quality. If there are no visible particles and the fluid has a fresh red color (slightly darker than new oil is normal) and there are no oil sludge at the bottom of your pan, your transmission is just fine and you have changed the fluid in time. Also use your smell, the fluid should have a sweet smell and not smell like excessive burnt oil. If  you find a very tiny amount of metal particles and no sludge in the pan, your transmission is probably fine too, but the mileage of the car is starting to show and you should consider finding a replacement transmission. If there are both particles and the oil is very sludgy and of dark color, then you probably have noticed some shifting problems already. Also the fluid change have been long overdue and the clutches are starting to wear out. Decide if you should change or service your transmission!

transmission oil pan w123
Inspection for metal particles and sludge in the oil pan. The oil here had a sweet smell and was only a bit darker red than new oil which is perfectly normal. In the picture it might look that it had some metal particles but it is simply some dirt that fell off from beneath the car and my sloppy handling before I managed to take the picture.

In my car, the pan was empty of particles and sludge, the oil also was very red and clear still after many years as seen in the picture, however I did not drive the car a lot either the last years since it has been in a “project state”. The shifting is super smooth and I have not encountered any shifting problems. These transmissions are usually rock solid and will outlast the car itself, only if however if the fluid have been changed at regular intervals.

Cleanliness

Clean the pan very throughly with some brake cleaner, wipe it completely dry with no fluffs from paper hanging inside it. Use your palm to feel it is super smooth and no dirt traces are left. Now you can also clean the surface of the transmission where it meets the seal, so you can expect a leak free gasket around the pan. Do not clean the valve body though, just leave it wet with fluid.

Cleaned transmission oil pan w123
Cleaned transmission oil pan and new gasket

Installation and Refill

Fit the new filter and apply the new gasket to the pan.

Install the oil pan and do not over tighten the bolts to not crush the gasket, make the rubber do the sealing and not brute force. Use a crisscrossing pattern like tightening the lug bolts to ensure evenly distributed gasket. If you are OCD then you should use a torque wrench.

Now time is due to measure the quantity of oil you extracted. A leak free automatic transmission will not use any oil and this is the quantity you should use. Pour in exactly this amount into the transmission through the filler tube, which also happens to be the fluid level checking tube. You have to use a narrow funnel to avoid spilling oil over your (hot) manifold which will make a lot of smoke and can cause fires.

Filling transmissio oil 280CE
Fill transmission oil through the filler/measurement tube. Use a funnel

Inspect under the transmission to see if there are any leaks. Then it is time to start the engine. Let it go for a few minutes before you start engaging all the gears one by one. Do this gear cycling  3-4 times with a minute in between so the fluid can distribute itself within the transmission.

gear lever mercedes w123 280CE

gear level mercedes w123 280ce
Cycle through the gears 3-4 times with staying in each gear for about a minute

Level measurement

After this is done, check the fluid level again with the car running in idle. It should be some below the maximum mark, also it can also be slightly under the minimum when the transmission is not warm. The level will usually be below minimum when the oil is cold even when the transmission is filled with exact fluid quantity. The transmission oil heats up slower and you need to go for a drive to get the right operating temperature, and the fluid will start expanding reaching to the recommended level. Check under the car again now while car is running to be sure there are no leaks. Then go out for a spin, drive at least 24km at normal cruising speeds. Do not race or do any high RPM of the car. When coming back after your drive the oil should have reached the right operating temperature. Remember to keep the car idling when checking the fluid level again. If the fluid level is still under the minimum mark, fill more ATF slowly and re check until it reaches between min and max level on the dipstick. If it is already this level, then you have filled the right amount and your car has probably not leaked a single drop between oil changes. Normally you have to refill some after this test drive so the level can reach the desired level between minimum and maximum, older cars have a habit of sweating slightly some oil through old gaskets.

If you over fill, so that the level is above maximum, do not panic! Then you have to suck out some fluid from the filler tube with some brake bleeder tool or similar oil extractor hose. It is critical that the level is between the max and the min mark, since little fluid can make gears slip and wear out the clutch material, and too much fluid can make to much pressure and your transmission might start leaking from gaskets and the oil can start foaming.

The only big difference here between engine oil and automatic transmission fluid, is that the transmission fluid has to be warm and the engine has to be running while checking the level. The engine oil can just be checked while parked and also when the engine is cold. If you happen to check your transmission fluid and forgot to turn on the engine, you would swear and rip your hair out since it looks like there is too much oil, then you turn on your engine, and while the fluid is still cold it looks like it is too little.

-> Correct automatic transmission oil measurement is when fluid is warm with engine at idle 🙂

Cheers, Robs out!