Clunk From Rear Axle Binding?
 

I've been hearing a clunk, clunk, clunk coming from the right rear side of my 380sl with over 200k miles on it periodically after decelerating and coasting at low speed, but not on turns, and a single clunk occasionally when shifting into reverse. So, I jacked the wheel up, and shook it with my hands above and below it to see if it had any play in the bearings, which it didn't.

OTOH, when I tried to move the homokinetic's axle shaft medially and laterally, I had to use two hands and a lot of force, which produced a clunk that seemed to be similar to those I've been hearing. However, the boots are intact, and I couldn't rotate the shaft at all.

The torsion bar, connecting links, control arm bushings, flex disk, and other possible sources are all good. So, I'm wondering whether to go ahead and replace the axle or not.

Before I do, however, I was wondering how much force it should take to move the shaft medially and laterally when the wheel is up or on the ground , and whether moving it from one position to another should produce a loud clunk or not.

Thanks very much in advance for any info on this or other ways to confirm my diagnosis.

Steve

I think you've probably found the culprit - the axle is probably knocking. It is difficult to say how stiff an axle shaft should feel; the best thing to do is to remove the axle from the vehicle and check the torsional wear at several points along its "in and out" position. There are a few videos of this procedure on youtube such as this one =>

How to Test a Mercedes Rear Axle for Excessive Wear - Kent Bergsma - YouTube

Stretch, thanks for the tentative confirmation, and the link to the video, which originally led me to suspect that the axle was bad. However, I was trying to avoid having to remove it until I had a replacement, and I didn't want to get a replacement until I could confirm it was the axle.

Ergo, even though the video said it had to be removed to test it, I was wondering if I could tell it was bad without removing it. And you just did that to some extent.

Accordingly, I guess I need to look around for a good used axle or a rebuilt one, since the new ones I see advertised seem to be Chinese junk.

It is harder to check the axles on the vehicle - if you raise the vehicle and then lift or lower the trailing arm into different positions you can get the axle to be in different "in out" positions and then you can wiggle / twist the ends to see if there is excessive wear: BUT! Because the axle cans are constrained it is possible to miss the greatest wear spot. It is much easier to find a problem with the axles removed.

As for replacement axles - well vstech (DD moderator) sells rebooted second hand units. Most people report good things about GKN axles. If, however, you get the annular axle type make sure you fit the bolts with loctite. (There have been reports of these bolts coming loose - this is the inboard differential end)

swap sides. they're the same and running in a different direction puts the joints on new surfaces. and if the clunk moves to the left, you were right. btw, had an sl years ago with a clunk on reverse then forward. the rotor on the rt rr wasn't bolted to the hub and you could see the hub move, making the noise and the rotor clamped by the caliper. the wheel doesn't trap the rotor as well as i thought. good luck, chuck.

I ended up taking the car over to a indy who specializes in German cars, and he confirmed that it was the axle as soon as he heard the clunk. Plus, it appears that the other axle is also starting to clunk. So I don't think swapping them would be the way to go.

I thought of that, but it doesn't appear to be the case here.

Thanks, Chuck