Guru's... Need help with vibration diagnosis

[talltorontoguy]

Hi guys, long time no see.

My 92 535 5 speed has an oscillating shimmy that comes through the seat. The shimmy is noticable at pretty much all highway speeds above 45mph. It gets more pronounced the faster I go, at 100mph it is pretty obvious (things shake in the car). Over that it gets a bit scary. I gave up on this quite awhile ago, but now I'm after it again.

If I press in the clutch and let the car coast, the vibration is still there, although less pronounced. I thought driveline vibration occurred under load so this doesn't make sense to me. Wheel vibration would occur at specific speed ranges, and it's been there through 4 different sets of wheels and tires so I don't believe it to be wheel/tire related.

A few years ago one of my rear wheels came partially loose after a wheel swap (thanks to my garage). I managed to stop before it came completely off, but it was askew and it did chew up the lug holes and center hole a little (I'm not using those wheels any longer). Could it be that this incident caused a slight bend in something in the rear end?

The vibration oscillates, and at 80 mph the peak to peak is about 2.5 seconds. (peak = max vibration) Don't know if this helps, but it might.

This isn't a thrust arm or other front end issue (been there done that, several times).

Is there a recommended diagnosis methodology to get to the root of this problem?

It's driving me nuts! Help!

[vince]

I would doubt if the wheel issue is affecting the car. While it could be a bent wheel or strangely worn tire, I'd put my money on the guibo being old, the driveshaft splines, center bearing and/or the driveshaft u-joint bearings. When under the car, check the guibo carefully for cracks. The center bearing is hard to access without removing the exhaust, and it's best to just replace it then. Driveshaft u-joints are hard to check well, as small amounts of play that seem insignificant can add up to something you can feel at speed.

I'm no expert on E34s, just spent too much time playing with BMWs the past 10 years. Maybe others can chime in?

vince





Hi guys, long time no see.

My 92 535 5 speed has an oscillating shimmy that comes through the seat. The shimmy is noticable at pretty much all highway speeds above 45mph. It gets more pronounced the faster I go, at 100mph it is pretty obvious (things shake in the car). Over that it gets a bit scary. I gave up on this quite awhile ago, but now I'm after it again.

If I press in the clutch and let the car coast, the vibration is still there, although less pronounced. I thought driveline vibration occurred under load so this doesn't make sense to me. Wheel vibration would occur at specific speed ranges, and it's been there through 4 different sets of wheels and tires so I don't believe it to be wheel/tire related.

A few years ago one of my rear wheels came partially loose after a wheel swap (thanks to my garage). I managed to stop before it came completely off, but it was askew and it did chew up the lug holes and center hole a little (I'm not using those wheels any longer). Could it be that this incident caused a slight bend in something in the rear end?

The vibration oscillates, and at 80 mph the peak to peak is about 2.5 seconds. (peak = max vibration) Don't know if this helps, but it might.

This isn't a thrust arm or other front end issue (been there done that, several times).

Is there a recommended diagnosis methodology to get to the root of this problem?

It's driving me nuts! Help!

[BillionPa]

rear wheel bearing could be shot.

[talltorontoguy]

I guess it "could" be bearings but normally I would expect a droning noise when turning to go along with the vibration. I'm not getting that.

Anyone else have any thoughts?

[shrike071]

If the wheel was loose enough to wobble, there is a slight chance that it may have bent the flange that the wheel bolts to by just a tic. That would give a vibration that no amount of balancing would cure. I'd also give the u-joints a close inspection - they can make all sorts of strange vibrations and noises when they start to go.

[talltorontoguy]

Hmmm, not bad idea. I'll see if I have one lying around to swap the flange out.

Any further ideas guys?

[Ross]

My guess is rear susp attatching points loose or bushings shot. Does it feel like the rear is steering the car?

[talltorontoguy]

No, I'm not getting rear wheel steering that you would find from worn rear parts. Car has new rear shock mounts, newish dogbones, new rear shocks.

Would the subframe bushings manifest in such a vibration?

[markus]

also check engine and trans mounts, they can cause a vibration also. But usually thats more of a low speed thing.

[Ross]

The shimmy part led me there. Perhaps a driveshaft issue then.