paul.parry

I solved a vibration issue that has shown up here from time to time. The vibration occurred when cold and lessened as the car warmed. I replaced the front engine mounts and this lessened the vibration but it did not solve the problem. I replaced the hanger bearing on the driveshaft, the universals and the couplings at both ends. This work made no difference. There is a shim in the differential mounting that I removed and this made a significant difference for the better although when the car sat for extended periods the vibration would return although at a lessor level. We then carefully checked the rear end and found slight weeping of the error sub chassis mounts. We removed the sub chassis and replaced the mounts. We re-fitted the diff shim and problem fixed, drives like a new car. The car has only travelled 14,000 kms as it sat in a shed for 12 years. The hydraulic mounts had all deteriorated and replacing these removed all vibration issues. Thought you might like to know if you are trying to solve a vibration problem.

ddb

I replaced the same list of items attempting to solve my vibration issue. They helped, but didn't solve the issue. I then removed the shim that you describe and it was a night and day improvement. I later changed the subframe bushings which improved the ride quality immensely. I've thought about replacing the shim (4 mm in my case) to see if it would further improve the vibrations after replacing the subframe bushings but haven't yet done it. After reading about your experience I will reinstall the shim and see what I get. Thanks!

armaniE55

Hmm interesting. I also have the same exact issue when the car is cold. I have replaced flex disc along w/overhauling the entire front end to no avail. Can you link up a part? I'd like to tackle this project. I feel that after changing out my inner/and outer tie rods I'm ready for anything (took me about an hour of heat to remove the inner tie rod on one side)

Easy to change out? DYI anywhere?

thanks!

Armani

ddb

Armani, yes, it is easy. There's an allen head bolt (IIRC) facing down towards the ground with something like an 18mm nut on top that has to be removed. Once the bolt is out you can remove the spacer and replace the bolt. What you're probably doing is compensating for deteriorating subframe bushings. It is easy enough to remove the spacer and see if it makes a positive difference. If not, it is easy to reinstall.

The link below started as a motor mount replacement and evolved into me removing the spacer. In the thread you will find a link from the UK that gave me the idea to give this a try.

https://mbworld.org/forums/w210-amg/...nts-today.html

armaniE55

Awesome... Thank you for the detailed description and link. Another quick question I apologize in advance if this sounds like a silly question. Are you not replacing the part/bushing/spacer? I haven't clicked on the link still at work

ddb

Not silly at all. No, at this point you're not replacing the spacer (shim). What you are doing by removing it is adjusting the pinion angle to compensate for something that has deteriorated, most likely the rear subframe bushings. In my case, and the case of the original poster, paul.parry, we've already replaced the subframe bushings. By reinstalling the spacer (which I haven't yet done, but will do tomorrow) I will be setting the pinion angle back to OE specs which should work well with fresh rear subframe bushings. The spacers are installed at the factory in whatever size is needed: 1, 2, 3, 4 mm identifiable by the notches seen on the spacer.

I think the general takeaway on this is: if you are feeling abnormal vibrations in your steering wheel, seat, gear shifter area, it may not be something in the front end causing it, but something in the rear of the car.

armaniE55

Ahhh

Interesting findings.. I'm going to remove it this weekend. Now my last question is if it does improve do you replace the existing shim or it's ok to use the current one after things have re settled if you will?

ddb

If the vibrations go away or improve dramatically you just leave the spacer off. If you later replace the rear subframe bushings or something else that was worn you can reinstall the same spacer and see if it further improves NHV.

Let us know if removing the spacer helps or not. Ask any questions if you need to.

desired_speeds

I took out the spacer and I still have the vibration. I think it's gotten worse actually. I was ready to buy a replacement driveshaft, but maybe I should change out the rear subframe bushings first???

ddb

Where exactly are you feeling the vibrations? Have you replaced or had a good look at the flex discs, transmission mount, or driveshaft center bearing? Of course it could actually be something in your front end like LCA bushings.

It could be your subframe bushings, but I wouldn't think so just because my experience was different. Removing the spacer made a huge improvement as far as vibrations. Then later on the rear suspension felt like it wasn't working at all (not a vibration issue) which led to me replacing the subframe bushings, which solved that problem.

armaniE55

Will report my findings... crazy that this little shim could play a big role re: vibration. I also did my driveshaft center bearing along w/tranny mount when I did the flex disc.

Thanks for the help

*I'm glad this topic was brought up as I was planning on re-balancing my wheels for the million time

armaniE55

Will tackle this today. Few quick questions:

Do I need to have both L\R rear tires on jacks or only one side?

On one post you stated that you removed the rear panel I'll do the same for easier access.

Lastly what was the torque spec you used?

Any other tips

Thanks and posts in the other forums really did help

Armani

ddb

I only jack up one side using the side jacking puck. Typically I jack up the driver's side because I have more room on that side. Today (now), I'm jacking up the right side because you are better positioned on that side to do the work.

The bolt head is 8mm hex and the top nut is 17mm. I use an articulating head, ratcheting wrench on the top nut because it can be somewhat difficult to get to.

Yes, by removing that box (10mm bolts) that protects the rear level arm for the headlight aim gives you a lot more room. It can be done without removing the box and I'm not removing mine to put the spacer back in.

Once the bolt is removed, you can lift up on the rear end yolk a little bit to give you enough room to slide the spacer out. It may be stuck due to being there for so long.

I don't have a torque spec unfortunately.

Off to reinstall my spacer. Will check back in later if you have any questions.

armaniE55

Awesome! Thanks.. report back your findings when you re install the Shim

Armani

ddb

Shim reinstalled. There's not much room to work, but once you do this the first time and know what you're doing, it only takes a minute. It takes more time safely jacking and securing the car.

You will also need a 6" or so extension to reach the 8mm hex bolt head.

I don't think it was any easier jacking up the passenger side. With the jack in the way, a jack stand under the LCA, I didn't have any room to slide under from the side. I did have plenty of room from the back of the car. The down side of jacking from the driver's side is by the time you slide over to the center of the car you start running out of room because the passenger side is on the ground.

Off to wash the filthy car. I will drive it this afternoon/evening and report back.

Give us some feedback once you're done.

ddb

Armani, did you remove the shim? If so, did it lessen the vibration?

After reinstalling mine and driving it yesterday, the car felt great. Maybe minimally better than without the shim. I need to do some more high speed driving to see how it feels. When I first removed the shim, prior to replacing the rear subframe bushings, I bought a 1mm, 2mm, and a 3mm shim to try out. Each one, going up in thickness made the vibration progressively worse. Now with the new subframe bushings, reinstalling the original 4mm shim definitely didn't hurt. I'm going to replace the 4mm with the 3mm just out of curiosity to see if I can detect a difference.

armaniE55

Hmm, interesting findings. Thanks for reporting back. I actually had a 4 wheel balance yesterday and when I left the car was still cold and sure enough a little shim and as I drove her closer to home it almost all away? After breakfast I'm hitting the garage to remove said shim

And test drive. Gives me an excuse to hit up Harbor Freights

Armani

Solo wing

*subscribed
Waiting for your feedback. Good luck

armaniE55

Gentlemen,

So last night I was removed the shim. First, the top bolt was at different size but I was able to remove it using a 17 MM closed wrench. I also removed the black shield as well to get a little more space. In addition I was able to match up the top bolt to the correct SAE wrench. Making a lot easier to close afterwards. Took a while and hands were cramping a few curse words and it was finally removed. I also had to use a flat head w/a tap of a hammer to knock it loose.

Now for the results

I took the car for drive as soon as I put her back together and first impressions were no shimy, turbulence from the cabin on cold. As I stated prior the car would always shake when cold and smooth out when warm/hot. So far I have to say that I won't be replacing the shim as she is nice and smooth right now.

Let me know if you have any questions..

*picked up a vice after my re install

Armani

ddb

Armani, sorry about the confusion with the top bolt size. Mine is definitely 17mm. In one of those threads I believe others had 16mm bolts.

Yea, it is difficult to get the spacer out for the first time. It has been in that position for around 15 years. Once out, it will go back in and out really easy.

Glad to hear it seems to have helped. It is amazing that a 4mm shim changes the pinion angle enough to rectify the vibrations. The big question is what changed to necessitate an adjustment to the pinion angle? In my case, and that of the original poster, it seems to be failing or worn subframe bushings.

Let us know if it keeps working well for you.

armaniE55

No worries at all. It comes w/the territory of being a back yard DYI. That's what makes it fun. Thank you for the hlep

Did you reinstall yours ? and agree the mechanics behind this one is very interesting.

Armani

ddb

I did. After driving it for a couple of days, at speed, I can feel increased vibration in the shifter area. The steering wheel however feels great. I think I'm going to try the 2mm shim next. I won't hesitate to go back to no shim if that provides the best results. Unfortunately I won't have time to work on, or drive the car until the weekend or early next week.

armaniE55

That's exactly where I noticed most of the vibration (shifter area) Sounds good keep us posted I would like to know the end result .

Thanks again

Armani

ddb

With the original 4mm shim back in I had vibrations in the shifter area. Took it out and replaced it with the 2mm shim which was an improvement. I now have the 1mm shim in and it feels good. No doubt it would be better with no shim.

So in my case I don't think my subframe bushings had anything to do with me needing to remove the shim to solve the vibration issue. I think replacing the subframe bushings solved a totally different problem and removing the shim is compensating for something else being worn out.

My guess is it might be a worn differential mount (bushing). I have the needed items on order to replace the mount. If the parts arrive this week I will attempt to do the replacement this weekend. I will detail the process and report my findings.

desired_speeds

Vibrations are felt in the steering wheel from 35-55mph. 60-65mph there is a humming noise from the rear end that vibrates through the cabin.

Engine mounts/ trans mounts, LCA bushings, ball joints, inner tie rods, front sway bar bushings, shocks, springs have all been replaced. flex discs visually check out and I'm sure it's not the center driveshaft bearing because it only vibrates in that range that everyone else gets it. 4 sets of wheels/ tires perfectly balanced and aligned and there has been no change. I took out the 4mm spacer and the vibration got a little worse.