W124 rear diff mounts inspection - PeachParts Mercedes-Benz Forum

ps2cho · #1 09-13-2011, 01:26 PM

For my 87 26E

I have a vibration on the freeway @ 70mph LOAD ONLY. It disappears when I get off the gas...its not a rim/tire issue. I also feel like my rear end is sagging too.

I checked center support and rubber looks good, so I wanted to check rear diff mounts.

What exactly am I looking for? Anyone got any pics of a bad diff mount? I searched all over the site and cannot find much -- just a few threads.

I'm new to all the axle stuff, so it may seem like an elementary question.

Thanks guys

lithium726 · #2 09-13-2011, 07:24 PM

I had severe vibrations at anything above 40mph, only under load.

You'll want to replace your rear subframe mounts, that helped me considerably. My next step (since I still have them, just not nearly as bad) is the center support bearing for the driveshaft. If your subframe has been moving around (likely the mounts are shot due to age) then your diff has been moving around and putting strain on the center support.

The rear subframe mounts are at the four extreme corners of the subframe (diff carriage) look for four large mounts which bolt up into the chassis behind the rear wheels (if looking at the side of the car straight on)

Air&Road · #3 09-13-2011, 07:42 PM

I've seen pretty bad diff mounts that didn't cause a vibration. Get a jack under the diff &move it up&down. You will easily see if mounts are bad.

benzme · #4 09-13-2011, 07:50 PM

The diff mounts in my TE were so bad you could see daylight through the bottoms of them. But no vibrations only a bit of clunking.

The sedan vibrated like that and it was the flexible coupling.

ps2cho · #5 09-14-2011, 01:10 PM

Even if the rubber bushing on the center support bearing is OK, its still possible the bearing itself could be causing the severe vibrations?

Here is a shot of one my subframe mounts from a year ago....I'll check them all out soon as the damn rain stops here!

I know I see a hairline crack, but other than that, do they as far as the photo goes, look reasonable?

Air&Road · #6 09-14-2011, 01:16 PM

RAIN! Don't worry about the rain, just send it down here! We're in the worst drought since the REALLY bad one in the early fifties.

To the bushings, I can't tell much from the picture. I have to use the 4 P's to check them; Push, Pull, Pry and Prod.

I was answering from my IPhone so I'll add details. In my experience, bad diff mounts result in clunking, not vibration. If you don't have a jack to move it around, if you can get the car up high enough and blocked up safely, just grab the front of the diff at the pinion and hang on it. Yank up and down and if the bushings are bad you will see and hear that they are loose.

If you have to replace the diff mounts, make or buy a GOOD puller and get ready for a work out. Also consult the FSM and make sure you orient the bushings correctly or they will be short lived.

Hope this helps,
Larry

ps2cho · #7 09-14-2011, 10:33 PM

Got some shots of the diff mount....

Don't they look cracked?

JohnM. · #8 09-14-2011, 10:37 PM

My subframe bushings looked like that too from the outside. They looked like this once they were out. It felt like the rear wheels were about the fall off in some turning situations.

ps2cho · #9 09-14-2011, 10:39 PM

I've lost my locking lug nut key so I'm gonna have to get it removed by a tire shop, so once that is done, I'll pop my wheels off and try to get a better look at the mounts.

Looks like its ~$125 total for all 4.

I've read its not that difficult to drop the subframe and remove the bolt -- the hardest part is removing the old trashed subframe mount, and pressing the new one in. How did you do yours?

JohnM. · #10 09-14-2011, 10:47 PM

Subframe only needs to be partially lowered, the job isn't that bad. Here's another good pic of my driver side mount. The core of the bushing fell onto the ground when I took the bolt out. Keep in mind both of these looked "good" from the outside. Only one had minor cracking like yours.

I did a write-up of the job for another member via PM, let me find it.

balge · #11 09-15-2011, 04:24 AM

I knocked my old diff mounts out by slitting them with a junior hacksaw them folding them up with a pointed drift. Made a puller out of some penny washers and studding, no real problems. Your diff mounts do look like they are separating.
Make sure to put the new bushes the right way up!

Air&Road · #12 09-15-2011, 07:06 AM

I'm glad that the method balge used for the diff mounts works, but I would highly suggest a puller instead. The subframe is sheet metal and you must deal with it carefully.

My brother in law, who is an MB dealer tech, and also a hobby machinist, made a puller on his metal lathe. The techs in the shop borrow his puller rather than using the MB provided one. If you know someone with access to a metal lathe, making a puller would be your best bet.

Good luck,
Larry

balge · #13 09-15-2011, 11:50 AM

The bushes aren't all that tight a fit. The accuracy of using a puller is helpful, but not necessary, a good hand and eye do well enough ..saying that, if I had a lathe handy, I probably would have made a puller myself...