500E Rear Diff Problems?
 

I've been having a clunking noise at the rear of the car whenever I go over bumpy roads. It started on the left side and now it's on both sides.
The MB dealer had a look at it when they did the 100k miles service yesterday and they say it is caused by the drive shafts being somwhat loose in the rear diff. The only way they can be sure is to remove the whole lot and open it up and further investigate. In the worst case they say I have to replace the rear diff which is going to be very expensive.
Before I decide what to do further I'd like to hear some opinions from the 500E experts if it could be something else or if if it could be a replaceable part inside the rear diff.
The MB dealer assures me it is not the rear shocks, they function okay and there are no leaks.
I find it strange however that I only hear this noise when I go over bumpy surfaces. It seems to me that if the driveshafts are somewhat loose you should hear that all the time.

Flavio

Hmmmm....I'm inclined to agree with you, Flavio. How many kilometers on the car, BTW?

I'm quite inclined to think it's one of the shocks-I've been there, with EXACTLY the same symptoms, and it was a shock. Since I didn't believe it either (no leaks, car rode nice), I went to the trouble/expense of replacing my shock upper mounts, to no good outcome.

Is it one side or the other? Have the shocks ever been replaced?

Michael,

The car has run 100,000 miles. The noise is on both sides. I don't know if the shocks have ever been replaced, I've got the car a couple of weeks and there is no detailed history.

Flavio

So you were saying it was on one side, now it is on both sides. Does it do it when you make turns, right hand or left hand? Can you remember back when it only made the noise from one side? Because sometimes the CV joints wear out. Maybe you need new half shafts.

I highly doubt that you need a new rear end, let alone that they have to adjust the play inside the differential from the axle shafts to the splines in the differential because they dont move. I know in W126 cars they dont move for sure, but I am not sure in the 500E, but I just looked in my service manual CD and it doesnt look like it either.

Maybe someone else has more information.

Austin

You only hear the clunking noise when the road is uneven and bumpy like when you drive over a pothole. You don't hear it at low speed or when turning.

If it is the shocks that are at fault is it possible to see something from the outside without replacing them and risking that it is something else?

Flavio

Flavio,

No way to tell externally if a shock's bad in the way you describe.

I really think, if I were you, I'd replace the one that's been making the most noise; have a friend ride in the back seat & tell you which side is louder.

I'm thinking a shock that sells for around 815 guilder/370 Euros is cheaper than pulling your diff and investigating...that could get real expensive :rolleyes:

Good luck

I have had this on the 16v which Im pretty sure has the same rear suspension set up as your car. Check all the rear suspension rubber pieces and especially the trunion joint which is on the outside of the lower control arm. It sounds to me like one of the rubber pieces has wore out and is causing this noise. Also have you checked the tightness of the rear shock top mount nuts?

I took it to the official MB dealer so I would hope they have checked that all out but I will ask anyway. Thanks.

Flavio

If the noise sounds like the upper shock mount is loose (which is PRECISELY the noise mine made-so much so that a factory tech replaced the perfect-looking mounts that were in there), then it's very likely the shock.:rolleyes:

Is the rear shock for a 500E the same as for other W124's with self levelling suspension? I doubt it but a reputable Mercedes parts supplier says it is. Does anyone have a part number?

Flavio

It is absolutely a 500E-specific part (and here in the U.S. I believe there was only 1 part number for the entire production run).

I can't put my hands on the P/N readily-perhaps someone else can help

Also check...
 

I'd also check the plastic connecting links from the control arms to the sway bar. They are a weak link being made of plastic etc. and very inexpensive to replace. Also check the sway bar mounts while you're in the area, although improbably defective. Doubt if it is the diff if quiet when shifting from drive to reverse etc.

If you think it's a shock, just remove it and drive over a known area that induces the knocking noise. Won't hurt to drive a few miles with no shock if the noise is that bad. You may want to try an independant shop for a second opinion and maybe less expensive for the parts and labor.
Just my two cents or 2% of a Euro!

Tobias MB
4 MBs