I have a 99 ML 320 with 165K miles. Last month I changed the rear shocks. (Thanks to everyone here who contributed postings on this subject.) I feel a moderately firm "thunk" or "thwup" in the right rear whenever I roll over even a small pothole or bump in the road. It's not very loud, and I can't say I actually feel it in the drivers seat. But it is definitely there and it's definitely coming from the right rear. It kind of sounds like either the spare tire or the jack is loose. But I've checked both and both are firmly secured.

I followed all the great advice from this forum to R&R the shocks. This job is not easy, but it's not rocket science either. If you can get to all the fasteners and have the tools to break them loose, you can do this. As far as I can tell, everything can only go back together one way. I torqued as many of the bolts as I could in my original work. (Couldn't reach the top three 13mm nuts with a torque wrench.) Made sure to torque the big lower control arm bolts with the weight on the suspension. I went back and re-checked all the bolts to make sure they are tight. I'm _pretty sure_ I did the job correctly.

I got my shocks from Fastlane. They are Bilstien part number BE52985 per the receipt I have from Phil. These are the shocks without the coil spring installed. I had a local mechanic swap the old springs onto the new shocks for me.

Do you think this is the correct shock for my truck?

How do you know how far down to run the top nut on the shock when you install the coil spring? The mechanic that swapped the springs had trouble removing one of the top nuts. He used an impact gun to install the new nut. At some point, the shock shaft just spins so you can't tighten it any more.

Do you think rear sway bar bushings could be the cause? Mine are original.

I don't recall seeing bump stops in the packaging. Is it possible I left out required bump stops?

Do you think the top three 13mm nuts are not actually tight on one side because, with the vehicle on jack stands, the rear suspension is pulling down as you tighten these nuts. I don't think it is possible to access the nuts with the weight on the rear suspension. Just a thought.

Your vehicle does need to be grounded when you tighten all the nuts and bolts associated with the shock replacement. You could try setting the rear of the truck on cinder blocks, assuming you don't have access to any type of ramp system, and that will give you enough height to get under and tighten everything. As for the rear sway bar, 2 of each: http://www.trademotion.com/partlocator/index.cfm?action=getLocator&siteid=213951&chapter=ERI5768&appSectionid=2788&groupid=51856&subgroupid=2544&componentid=0&make=67&model=M%20class&year=1999&graphicID=5768500&callout=3&catalogid=2
I did mine along with the shocks and had positive results. I'm not saying that is your problem though; good luck.

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Steve32

Interesting. I knew from discussions on this forum the axle shafts had to be parallel to the ground while tightening the lower control arm bolts. I did that. Didn't realize _all_ the other bolts and nuts had to be tightened with the suspension loaded. I did all the other bolts while the truck was still on the jackstands.

I'm anxious to find out if I can even get my medium size hands under the frame rails to access the three 13mm nuts on top of the shocks with the suspension loaded. My expectation is there is not enough room unless you lift the truck and let gravity pull the suspension apart a bit.

I'm also going to replace the sway bar bushings.

Thanks for the response and link.

I wouldn't worry about the three 13 mm nuts on the top of the assembly. As long as they were tight when installed, they will be fine. They are self-locking and with the weight of the vehicle on the coil/shock, stress should be reduced.

FYI...........I took my ML to a friendly TiresPlus and had them torque all suspension pieces to proper specs. They used an alignment rack which was perfect..gets vehicle up off the ground, but still has weight on the tires.

Your 'thump' is very likely the upper shock bushes....If it did not do this with old shocks, refit the old upper bushes.....
I had this with a self leveling e320 wagon a few weeks ago....the new upper bushes where too thin to absorb the wheel movement..ie : there was not enough compression of the bushes with the top shock nut fully tightened .....I installed other bushes I had in the shop from other shock jobs that had fat bushes....took some compressing to get the nut to start but no more noise .

This problem is known to affect some other Mercedes too.


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dkveuro -- Thanks for the suggestion. I don't have the original shocks any longer. Do you know if these bushings are available by themselves? And from what source?