phil240

Here's a mini write up for you guys that are interested in doing this yourself.Now there is no interval for changing your rear diff fluid from MB,but it is an oil that should be kept up with under regular maintenance.I would suggest changing it every 50k miles as i just did my change at 64k and the fluid didnt really look all that bad.

MB does say to use a liquid thread sealer which is what is used from the factory but i went with teflon tape as it works just as good if not better.

Here's a list of items you will need to do the job:
2 quarts of diff fluid (i went with genuine MB but if fuchs makes it by all means)If IIRC it was like 27 dollars a qt
One can of brake cleaner
small manual fluid pump (10 bucks at auto parts store)
1 roll of 1/2 inch teflon tape
14mm allen head socket (mine was 1/2 drive)
1/2 drive ratchet
6 inch 1/2 drive extension

Here's some pics of the items you will need:





Now i took pictures of the drain and fill plugs in the diff itself for varification purpose.

This is the drain plug on the right side of the diff (passenger side)




And here is the fill plug on the left side (driver side)




Steps for procedure:
1. once you get the vehicle up off the ground making sure its level,you will unscrew the drain plug on the right side with the ratchet and 14mm allen head socket.
Allow to drain completely.
Once drained you will need to put the plug back in but first you will need to wrap it with teflon tape,and oriented like so.

Alot of people dont realize that you can wrap teflon on a pipe fitting backwards.You also only need to wrap it about three times around.

Now you can reinstall the drain plug.there is a MB torque spec of 50nm or about 37 ft lbs,however i didnt use it i went till i knew it was tight enough.
The one thing you do have to watch out for is that teflon is a lubricant and you could over tighten,i suggest just either using the spec or go until its gets tight but not overkill tight.


Second step:
Now you can remove the fill plug,you will now need to use the 6 inch extension as the exhaust gets in the way.Once remove repeat the proper teflon wrapping step as described above.






Now you can use the pump and pump in the fluid.Fill till the fluid starts to come out of the fill hole,The MB capacity is 1ltr/qt.But the reason you need 2 is that you will lose some through the pump and what you cant pump out the vary bottom of the container.
Now reinstall the fill plug and torque to 50nm or 37ft lbs or till tight enough but not too tight that you overkill it.
Now you can use some brake cleaner and spray and wipe the diff down in the areas where oil is from the service that was just done.

Now you are finished with the rear diff service and i would give a recommendation of changing the fluid every 50k miles.

If you have any questions ill be happy to try to help.

-Phil

Carsy

A good write up. Thanks Phil.

ambit

It's a good idea to make sure you can open the fill plug before you drain it. Sometimes they're a ***** to torque open.

mleskovar

I would do one thing differently. Before draining the fluid first make sure you can loosen the fill plug.

phil240

You guys are right but!
But there is no reason that you shouldn't be able to,if you had to you could use a 1/2 inch breaker bar to assist in loosening it.

splinter

Solid DIY work, phil240.

I’ve had leak-free results from GM’s Teflon® sealant, if only because there’s plenty in the consumables bin.
And don’t get that spent fluid on any clothes you’re anticipating to wear again. It’s stinky. :)

Carsy

I reuse my heavy gear oil on my motor cycle & ride on mower chains.

All sump oil goes on timber fence posts to stop rot & deter white ants.

splinter

That's illegal in the States. ;)

Glyn M Ruck

Nice DIY - Thanks

GotDaBenz

You did a fantastic job with that DIY, and the pics were very informative!
Thanks a lot,

marioblackbenz

Hey thanks for this great post. My 2002 C230K 6-speed stick - 167,000 miles orig. owner ( purchased in July of 2011; - has a lot of noise back in the diff. 2 shops quoted me $1700, then $1300 parts & labor to switch out with a used diff.
I figured let me see what's back there. I went ahead and gathered tools and supplies as you suggest here, and when I opened the drain plug, I pulled out one small sheared off gear tooth!!!
Re-filled with new oil. Car is drivable - albeit slowly - but I wanted feedback if anyone thinks tearing down the diff and just changing out the gears. I'm strapped for cash, & both quotes are out of range right now.
Mercedes wants $3500 for new diff - a lot of dough, but maybe worth the cost versus installing a used part which may die sooner than later; who knows how many miles the replacement part has on it and if that car was driven hard.
I am based in the SF east bay.

Gersh320

It's called recycling . Good job, from the earth back to the earth

I used old oil to spill over a large puddle (small pond) last year that was spawning mosquitoes, killed them within a day.

Quick question though. I'm in the wrong W class here but I have a W211 that is about to hit 100k. I want to change the diff oil and have the spec sheet that calls for 85w90 that is the same for the C Class. Is this synthetic? Where can I get it of not the stealership? Brand recommendations?

bibauporto

Greetings,

I'm about to change the rear differential oil on my 2002 w203 C220 CDI, have no idea how bad it will be as I don't know if ever been changed (the car has now 315000km).

Can anyone tell me what the oil requirements. Will I be fine with FUCHS Titan sintopoid 75W-90 2L
Auto (API GL-5)?

Best regards

mleskovar

Unsolicited advice: Make sure you can loosen the fill hole plug BEFORE you drain the fluid. Drive for a while to get the fluid to flow better before draining. Any fluid that meets or exceeds the spec is good.

Gersh320

I went with the MB original. Cost more but will stay in there for the next 100k so not a big expense taking that into consideration.

VVF

+1 on the OEM fluid. I bought 2 bottles, used 1.2 probably.

faran

I must say that your DIY is the best and very helpful and clear. I did it today on my 2004 CLK500, I used 'Pipe' thread sealant on both fill and drain plugs.

Also, used a 1/2" 14mm socket with a almost 2-2.5 foot long ratchet and cracking both bolts was a piece of cake.

Cleaned both plugs and used generous amount of carb cleaner after tightening them up.

I consumed almost 1.3L of MB original fluid. One word of advice(as mentioned everywhere), always open drain plug first, remove it and then remove drain plug. Old fluid will come out quicker and make your life easy.

Let me know if any questions. Thanks guys

slammer111

Thanks for this post. Very informative.

Did my first differential fluid change at 250k km. Might be a bit long, but never got around to doing it until now.

Things needed:
- ratchet or breaker bar
- torque wrench
- 14mm hex (male) socket
- 6" extension
- pump or syringe for filling differential pumpkin
- rags for cleaning up puddle, jug for old fluid, etc.
- 1.2L fluid (this is the bare minimum - just buy 2L)
- thread sealant (personally I recommend paste instead of tape)

As of the time of writing, MB recommend 75W-85 hypoid gear oil. I'm sure some aftermarket stuff will do the job, but I wasn't going to risk using the wrong fluid with such a critical component. The viscosity might be the same for an aftermarket fluid, but there is no way to know if it has the correct additives.

The PN is A001-989-33-03-09 for 1L. The dealer charged $95/L CAD ($70 USD/L) before taxes for this stuff. The relevant spec to match is MB-Approval 235.7. The most recent time I checked, there are only 4 approved fluids out there, 1 of which are from MB. Personally I was unable to source any of the other fluids from anywhere outside of the dealership, at a price lower than the dealership. Had to eat this one.


MB OEM 75W-85 differential fluid


MB differential fluid A001-989-33-03-09, MB-Approval 235.7

The new fluid is a bright orange/yellow, like diluted honey.

My understanding is that the W203 (non AMG) cars need 1.1L, so I picked up 2L. Ended up spilling a pile into the ground when I knocked over a bottle. Thank goodness I had extra.


Fill hole location, towards L side of car (14mm hex)


Drain hole location, towards R side of car (14mm hex)

As others have said, always remove the fill plug first, so that if something goes sideways, you won't be stranded.

Some recommend driving the car around a bit to mix up the old fluid and warm it up. Personally I think this is optional. The fluid itself flows really easily, and is only a tiny bit thicker than engine oil. I was actually expecting it to be more like honey.

Some also recommend spraying the plug areas with brake parts cleaner. Personally I just used a few wet rags. There actually wasn't much in terms of dirt or grease in the vicinity or threads. The rags were clean after a few wipes.


Plug with dirty fluid

The plugs are magnetic, so I was expecting to see some shavings or other debris. Both plugs had none. The fluid was very dark, but the viscosity was very similar to the new fluid. While some may say to change the fluid more often, I think 250k km is actually fine. In fact I probably could've gone longer if curiosity didn't get the better of me.


Plug with dirty fluid removed



Instead of using a pump or hoses for the new fluid, I simply used a large syringe. I'd actually recommend this method. The trick is to make sure the syringe OD is smaller than the neck of the bottle, so I was able to drop the syringe in and fill the cylinder. Also make sure the syringe is long enough to reach the bottom of the bottle. If the syringe is a bit too short, simply pour the remaining contents of a bottle into the next bottle, or pour into another container of choice.


Differential fluid syringe

For the thread sealant, I used some Permatex (high temperature) thread sealant from a local auto parts store. I did notice that they used a similar product (as opposed to a kind of tape) at the factory, which I was able to wipe off the plug threads. High performance stuff isn't needed here, as the differential isn't some high pressure application. I'd be more worried about temperature than pressure in this application.

As per the thread sealant directions, add a bead about 3/4 of the way around the circumference of the plug, covering about 1-2 threads, and starting 1-2 threads in from the end so that nothing ends up inside the housing itself where the fluid is. The stuff will spread out when the plugs are screwed back in.

Plug torque is 50 Nm, or 37 ft lbs.

If I were to do this job again, I would've been more careful with the funnel system for catching old fluid. Made a bit of a mess on the ground. The fluid will gush out (horizontally) initially, then slow to a dribble.

Lastly, did I notice any change in driveability after the fluid change? Nope.