Chasing Vibration, W210
 

1996 E300, 190K miles

So I have this humming, droning, throbbing vibration that starts around 60 MPH and stays at it up to 85, which as fast as I have driven it. The frequency changes with speed. I’ve been focused on the drive line, but all the changes I made have not made a difference. I’m beginning to suspect a rear wheel bearing assembly is to blame, but when I check them with the wheels off the ground they feel fine - no play, no rumbles or notchiness.

I can feel it through my feet on the floor, my butt in the seat, through the steering wheel, and through the console around the shifter. It’s subtle, though. My gut leans towards the sound coming from the rear end. Swerving right and left doesn’t make a noticeable difference.

I’ve dug around looking into both drive line and wheel bearing threads but they are all over the place in terms of symptoms and fixes. What’s worked for some has not worked for me. Here’s what I’ve done to the vehicle in the last year or so:

- Rebuilt rear suspension with new links, new lower control arms, new springs, and new carrier bushings;
- Fresh tires;
- New Bilsteins all ‘round;
- Rebuilt, balanced driveshaft with new u-joint, center support bearing and bracket, and fresh flex discs;
- Welded in front spring perches and rebuilt the front suspension while at it;
- Wheel alignments after each axle rebuild;
- New wheel bearings on front end, setup using a proper metric dial indicator;
- New engine and transmission mounts (installed last weekend); and
- Adjusted drive line angles by adding/removing shims at the trans mount, center support, and diff, and also by installing the fresh mounts.

So what the heck does W210 drive line vibration feel like compared to rear wheel bearing related vibrations, or even front wheel bearing vibrations? Someone out there experienced and fixed both in the same car?

And if you’re still reading you must really be interested . . . .

I found documentation on what drive line angles are supposed to be for W210 chassis variants (see attached pics). I took measurements where I could, between the trans and front section of the drive shaft, and between the front and rear sections of the drive shaft. I can’t find a surface on the diff that provides consistent measurements.

To get the angle of the transmission I measured off the bottom of the steel pan. I found multiple locations to read from that gave consistent readings. I used a magnetic digital angle finder that’s pretty sensitive. I made repeated measurements and averaged the results. I found that the transmission seems to sag towards the front, creating an out-of-spec angle between it and the front shaft. I hoped replacing the mounts would fix that but I only got a half degree out of it, leaving me with a measured angle of about 2 degrees + (should me more or less 0). Is it possible the steel pan is not level with the angle of the transmission, thus giving me a false reading?

Pull the drive shaft and have it checked out? Go ahead and replace the rear wheel bearings?

It sounds like you've tackled this methodically so far, nice work. Everything I can think of, you have already replaced. One trick for identifying a mystery vibration is to mount a Go-Pro camera under the car with a magnetic mount. Go for a drive to reproduce the problem, then come back and review the footage. Re-position the camera and repeat the process until you find the vibrating component.

I've read about people doing that. Another approach that seemed good, at least for checking out the drive line, was to put the car on a lift, rear wheels in the air. Run it up to speed and use a strobe light to to have a look. The strobe supposedly makes it easy to see components jumping around.

I'm considering finding a local shop that has that system of mics to position around the car and take a reading while at speed, then use software to localize the source of the vibration. What's it called? I wonder how much it might cost.

Had a similar issue with one of the W210's. Not as thorough as your work but ID earlier as a bent rear wheel. Had the local alloy repair dude do his magic and gone.

Not a w210 but I eliminated a similar vibration by clocking the transmission and drive shaft yokes 120 degrees years ago as per the manual.

I've thought about wheel/tire issues. When I had the tires replaced I asked the fellows in the shop to check the wheels out while they had the rubber off and the wheels were found to be true. These guys have caught and pointed out a bent wheel I wasn't looking for on another vehicle, so I trust their equipment and judgement.

Thank you for the reply!

Are you talking about simply disconnecting a flex disc from the flange and rotating the flange 120 degrees and re-attaching? Maybe doing this a couple times to try all three possible scenarios between the trans and diff flanges?

Probably worth a shot. I see after reviewing the drive shaft removal procedures for both W115 and W210 that there is a subtle difference between them. The W115 book doesn't mention marking the positions of the drive shaft sections in relation to the flanges they connect to. The W210 procedure says to do this. Relying on experience with older M-Bs I removed my E300's drive shaft without marking those positions, so the trans and diff flanges very well could be in different relative positions.

For the w124 yes you clock the yoke 120 if no difference another 120 if again no difference move to the diff and clock those. It worked for me on the second clock.

OK - that sounds simple enough. W124 is pretty much the same as far the drive shaft and rear end go. I thank you for the suggestion. I'm going to try it. I want to eliminate all variables I can before putting more parts into it, or before pulling the drive shaft out and taking it back to the shop.

FWIW I went through the procedures for checking W210 drive line angles in greater detail. Looks like you must remove the transmission's steel pan to take readings from a special location using a special adapter with the special angle finding tool! Still, I wonder about measuring off the pan. Another way would be to measure off the flange, something I will do while I have access to it while re-indexing the flange to the front shaft section.

Also pay attention to the washers on the bolts they can be although I never have seen them different thicknesses to weight balance the system. I can't remember but I believe they are available in 3 different weight thicknesses.

Today I got under the car and indexed the transmission flange 120 degrees as we've talked about. Took it for a drive and did not notice much of a difference between 60 and 70, but when I took it up to 80 it seemed to smooth out compared to before. I'm going to index it another 120 degrees again tomorrow and see what happens. If that doesn't get it I'll index the rear 120 and then go through all three positions up front again, and onward until I've fixed it or tried all 9 possible positions of the flanges in relation to the drive shaft.

Something else I did while under the car with the drive shaft disconnected from the flange was to take angle measurements from each of its three "ears", which ended up all being the same. Out of curiosity I compared the flange angle to the transmission pan angles. There's a section at the front of the pan that's at a different angle compared to the rest of it, and as it turns out this front section is exactly 90 degrees from the angle I got from the flange. I was using the rear section of the pan for my previous transmission angle measurements, and this accounts for the out of spec angle I was getting before. So now I measure -0.30 degrees between the trans and the front shaft section, well within spec, and set up to come back towards 0 as the mounts wear and the engine drops a little.

All fasteners, including the washers, came with the flex disc kits I got from Pelican (the OEM ones, German SGF IIRC). All three washers I had loose today look the same.

Thanks!

Look into methods of diagnosing and balancing drive shafts. I remember something like spinning the shaft while on the car and marking with chalk. It's been a long time and the details are forgotten.

My W123 CD had same type vibrations. Previous owner had changed motor mounts. I made a "plumb bob" and taped it to the drive line. Then measured straight across to frame. Left and right were off by about 5/8". Evidently he did not get the engine centered after replacing mounts. I loosened engine mounts, exhaust, center bearing, and tranni mount, lifted on engine and pryed the engine back to center. No vibrations, something easy to check.

I've read on other w210 forums about people claiming the diff gears or bearings can wear and cause vibration. Maybe use a listening device, or your hand, and see if the diff is vibrating when the car runs on a lift.