W124 differential mount R&R -- DIY?
 

Most W124s including my '87 300D Turbo hold the differential to the rear subframe with three bolts (the 400E and 500E are slightly different). The two bolts at the rear are cushioned in healthy rubber grommets. These, like anything else made of rubber and going on 25 years old, wear out. I'm trying to decide whether I can replace mine myself.


http://i323.photobucket.com/albums/n...ntial_8124.jpg


Of the two grommets in my car, the left one is the worst. With the car up on jack stands (rear wheels barely touching the ground), the weight of the differential hangs from the subframe and a gap shows where the left-hand rubber grommet is starting to fail. (BTW, the bottom of the grommet is supposed to be missing a section of rubber; the new ones do too.)


http://i323.photobucket.com/albums/n...-down_4713.jpg


If a jack is placed under the differential to take the weight off of the subframe, the gap in the grommet goes away. Clearly, the differential can move up and down this much during driving. The grommets should be replaced.


http://i323.photobucket.com/albums/n...ft-up_4712.jpg


The forum has a few threads on this subject, with varying opinions of its DIY-ability. None have much in the way of pictures or detailed instructions. The major problem is that the grommets must come out and go in from the front, not the rear. The differential must be lowered at least 5-6 inches to gain access. FSM suggests completely removing the differential, which requires much of the exhaust system and the rear half of the driveshaft to come off first. A special puller ($150) is required for grommet R&R although I should be able to do without it.

As a DIY project, this does not look like a lot of fun. As a shop or dealer project, it looks costly. The grommets are not expensive (~$25/pair); it's all a matter of labor hours. Given that the grommets are not yet completely disintegrated (no clanking noises or stability problems), I'm tempted to let it go for the time being. Your comments are invited.

Jeremy

R&R'ing the diff alone is a PITA even with the axles off because the vent hangs on the subframe. This is much more of a problem getting the diff back in place than working with gravity to get it out. Judicious application of brute force deformed the vent but didn't render it inoperable. If I had to do it over, I'd pull the subframe and do everything back there in one shot. Everything else is 25 years old, right?

There's a special tool for the diff bushings and you have to note and replicate how far into the tapered hole the bushings go. Not MB's finest engineering hour.

There's a debate as to whether the diff should support the weight of the car.

Sixto
87 300D

I have done it. I would rent the proper tool. I used a bolt/washer setup and it sucked! I only replaced one of them because I ran out of time, and it sucked. Dropping the rear frame sounds like the best bet, but your gonna need lots of replacement parts. Sounds expensive.

Ah ha! So we meet again.

My 95 has this problem too. The clunk was significantly reduced by adjusting the transmission a little bit. I am still thinking I might do this job. BUT it looks really tedious! I have being underneath vehicles.

Did you ever get around to doing this, or having it done, Jeremy?

I am doing this next weekend on a '93 300CE. I have the special tool (from SirTool) and new MBZ bushings on the way. I always take lots of picture, so I'll take notes too and put together a tutorial.

Photo the indexing/clock position of the old bushings before removal. Note/photo the order of the front mount bolt, washers, mount and especially the shim placement. The shim sets the pinion angle, if the angle is not correct due improper placement of the shim it will cause a vibration.

Good luck!!!

Just for comparison, I had this and the flex discs (while we were down there) R&R'd on my E300D a few months ago. Didn't realize how much it would improve drivetrain feel.

Anyhow, the whole jobs, parts & labor was $800. Right now, I have more $ that time or garage space.

I managed to get one bushing replaced (the worse one) awhile back, it was a PITA and I did not remove the diff.

My diff is leaking, I have a donor car that I can remove the diff from and put in my car- is it that big of a job? I was more concerned about removing the axles, already had the driveshaft/exhaust off for new trans not that big of deal in a shop with a lift.

New flex discs will do more if you have a clunk or poor shifting, my 95 E300 was shifting horribly and I thought it was the trans but the flex disc was almost shredded and putting a new one in was like a new car!

I got rid of the problem by selling it to Sixto and he put it on eBay and sold it to someone in Los Angeles. Don't think it was ever fixed.

My current 124 ('95 E300D) is OK so far in that department.

Jeremy

I need to do this on 95 E300 but I don't have the special tool. Did you buy the special tool ? If you did how much did you pay ?

you can use a few sockets in lieu of a special tool, I found the info somewhere online I forget where. My experienced tech cousin also looked at it and was able to figure it out. Good luck!

I have done this on my 300D. The differential will drop low enough to get the bushings off an on without completely removing it. You might need to un hook the exhaust doughnuts to allow the diff to fully drop down. Using the tool makes it much easier. I have the tool and several sets of bushings. I have rented this tool out in the past. Please PM me to further discuss.
Thanks,
Lee

PM sent

If anyone is looking for a DIY on replacing the differential fluid on their W124, please check out our tech article below.

Replacing Your Differential Fluid



-Dmitry

When you do this, be sure to take lots of pictures and be extra safe supporting the vehicle. Securely strap vehicle forward and back to prevent movement!