93 124 rear end knock / clunk
 

Howdy folks. 1993 300E, 2.8 - For the last couple weeks, I've noticed a pronounced "clunk" coming from the rear end when I go from reverse to drive while backing out of the driveway - it'll only do it if my foot is off the brake when I make the shift. Now yesterday I noticed that I'm getting a rythmic clunking from the same area when accelerating from a stop - only though about 5-10 mph under torque, then it disappears. If I accelerate very gently, it won't do it. Could be my imagination, but it seems worse if I happen to be making a turn while doing this. I didn't have time to get it up in the air last night, but I did look the CV joints over briefly and didn't notice any torn boots. If it is indeed a CV joint, I'll be relieved, but I'm very scared that maybe it's the diff because I noticed the rear end is wet with lube (although not dripping anything on my driveway).

Also, why is it that most of the parts houses only list/carry the "inner" CV joint - is that the more common one to fail? If it is a joint, am I better off getting an entire axle assembly or just the joint? New price is $900 and some change for the half-shaft - I think I've seen a few rebuilt units for around $300. Any thoughts on the issue would be most appreciated.

Check the rear and front Flex Discs at the ends of your drive shaft.

http://i179.photobucket.com/albums/w...ntflexdisc.jpg

Definately check the flex disks. The part is inexpensive, replacement isn't too bad a job, and it can leave you stranded. Also check out the differential mount bushings; these cars are about the right age for problems there. Of course, that would only give you a clunk when switching from drive to reverse. I haven't done it yet, but I understand this job is not quite so much fun...

The axleshafts just don't go bad. If the rubber boot is intact, I'd take that off the list of candidates.

- JimY

Well, I got a chance to get it up on a rack on Friday...checked the flex disks as suggested and both appeared fine. Could not find any slop or unusual play in either axle, driveshaft, or rear end. Rear end was slightly low on lube, but nothing that would be a cause for alarm (I changed the oil also, as a matter of course - no sign of metal). I had about given up when I noticed that the plastic "sleeve" around the right rear shock had slid down past the shoulder that holds it in place and was laying loose on the bottom control arm. I got to wondering if, at certain angles (like when accelerating) if the axle or CV boot might rub against it, causing it to bounce and make a thud / clunking noise. I put it back in place and shure enough...noise is gone! Funny how something so trivial like that can mimic something more serious. Sure had me stumped for a while, though!