I have a pesky vibration I can't figure out or get rid of. Originally the issue was my center support and u joint, so I found a used driveline in good condition and had it swapped out. It felt great after the switch for the first 1-200 miles and then started vibrating again. I then replaced the flex discs which had started cracking and the issue was again gone, and it felt better than ever.
Unfortunately, about 150 miles later, I now have a sporadic chirping and/or clunking noise when rolling. It doesn't happen all the time, but does seem to be getting worse. I also can't pin it to a certain speed range very well. The sound does sound like it's coming more from the back of the car than it did before, but I don't know what else to check.
I did roll the car back and forth a few times and had the wheels on the ground when I tightened the center support bolts. I haven't touched the 46mm bolt as I was able to change the flex discs without messing with it, but could that be an issue? I don't have that big of a wrench, so that's why I haven't tried that.
Could it be something other than the DL, like the rear end or the half shafts? I did notice that the boots are starting to crack even though they don't look that old, so I was planning to replace them when I can, but didn't really think that would be causing this issue.
Any advice would be greatly appreciated as everything looks good to me and it's really weird that it just started happening a couple hundred miles after replacing the flex discs instead of happening right away.

How are your engine and transmission mounts? Any torn/leaking axle boots?
Bad engine mounts will cause vibration. Also, is the vibration throttle dependent? I had a vibration when under throttle on the highway, it turned out my main fuel filter was getting clogged causing the engine to run rough.

wheel bearings?

I went through something similar with my 300SD years ago, IIRC it was related to the combination of collapsed engine mounts (including engine shocks) AND the transmission mount. I went through and did the flex disks, twice balanced the wheels even though it had been done when the tires were replaced shortly before, checked and re-checked wheel bearings, and everything else BUT the mounts. The trans mount gets forgotten about often, but it's easy to change and a good one to verify it's not collapsed.

Thanks for the quick replies.

Yes, the axle boots are starting to tear, but don't appear to be leaking. would that cause a vibration?

How do I check wheel bearings?

the tranny support looked okay, but maybe I don't know what a bad one looks like. I'll take a picture of it shortly.

oh, also, no throttle has no effect on the vibration, only rolling

Cheap things first. Remove the inner clamps on the outer axle boots and squirt a few ounces of heavy oil in. Cheap screw clamps to reseal the outer boots are okay.

No change loosen that larger driveshaft nut using a pipe wrench or whatever you have or can easily get. Especially if you got that driveshaft from another car and installed it without loosening the nut.

The adjustment it allows is basically to cover production differences. These are just a couple of cheap things to eliminate before going further. I do not expect this to eliminate the problem but might. In any event they have to be done.

good advice, thanks Barry. Any advice on how to loosen it, roll it back and forth, and tighten it with the suspension loaded? My friend has ramps I could use, but would it be safe to drive it back onto the ramps with the nut loose?

That nut was not too tight on the couple I have done. I believe I just used a pipe wrench but do not remember. I would want to make sure the splines slide fairly easily even if I had to remove one portion of the shaft and relube it. Marking the shaft well so the balance is not lost. Driving up the ramps is not going to cause any issue I can think of with the nut a little loose.

Just a mention for safeties sake. When applying pressure to the nut you are trying to turn the rear wheel. Leave the transmission in park. Block a rear wheel as well perhaps. I do not think any of us are that strong but better safe than sorry.

A set of channel Lock Pliers will work good on the 46MM large nut also.

Charlie

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there were three HP ratings on the OM616...

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80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

I had a terrible vibration/shaking at around 50MPH....

This was after I had been driving for around an hour at 70-80, and slowed down.

It turned out one of the Inner CV Joint gaiters was leaking and all the oil was lost. I packed the CV joint with CV grease and fitted new gaiter--the split-type you glue together.

That was three years ago, and around 30K miles by now. Its been fine ever since.....

--Noticed today--On MOT Test that the Other side inner joint gaiter is very cracked--looks like it may be a bit moist (difficult to tell,--Its been raining now for a month), guess I'll change that one too--the same way!

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

Thanks Alastair, good advice! Mine are cracking too I noticed so I'll have to do the same thing. I like the idea of a split one I can glue together so I don't have to take the axles completely off. Is that a generic part, or is there an application specific one to use? Do you remember where you got yours? Also what is CV grease? Is it specifically made for CV joints or would I should I just use Moly grease to pack it?

Thanks Barry for the help, I just loosened both the 46mm nut and the center support, moved it back and forth a few times and then tightened them both. The sound had already gone away this morning before I did anything to it so it's hard to tell if I fixed anything or not. Will continue driving it for a few hundred miles and see if the noise returns.

On intermittent noises one cannot ignore the rear outer cv joints. Many may not have seen a relube since they were new.

I almost see adding a couple of ounces of heavy oil as a maintainace item. Typically when they are getting somewhat dry they produce noises of an intermittent nature. Keep driving on them and the noise can become constant. At that stage the axle will probably need replacement. As a general rule as long as any noise from them is intermittent they will respond well to a relube.

Every time we purchase one of these cars it is my belief they should be done. It costs little and is very easy to do. Incidentally heavy oil was in them from the factory and it is superior to grease. The failure of many cv joints in other bransds I have changed over the years was a failure of the grease basically. There was hard stiff grease left in them but none was reaching the working components of the cv joints. I often wondered why other manufactures did not switch over to heavy oil as the joint lubricant. To a simple guy like me it just makes more sense.

So I oiled the half shafts as directed, but the noise came back. I noticed when I loosened the boot on the driver's side that oil started leaking out, but didn't see that on the passenger side. The passenger side is the one making the noise. Do you think it's worth re-oiling or does the axle need replaced? Anything else I should do to check it?

I'd say it's worth oiling the axle to see if it solves the problem. It's an easy thing to try before blowing like $100 on a new one.