Help! Heavy vibrations - The Unofficial BMW M5 Messageboard (m5board.com)

Frits · 24th October 2009, 09:43

Guys, I need some help here. We have an E34 M5 Touring in the shop, which has an annoying issue with vibrations.

It starts at speeds usually higher than 80 km/h. Haven't tried anything faster than 130 km/h. When you slightly hit the brakes, or go through a pothole, it can start. Not always. It starts with just an annoying vibration, but it keeps getting worse and worse, and a few seconds later the whole car is shaking. Yesterday I was driving it in the evening, with the lights on, and I could see the beams go from left to right. Even with no pedals pressed, it keeps on going.
I once tried to press the accelerator while it was vibrating, and it seemed to get better then. Not sure if it was just luck this time, or if it really helps.

Now, customer allready changed plenty of parts, all the bushes/arms of the front suspension, front rotors. We changed the front shocks too. Doesn't help at all...

We checked everything at front, but can't find anything. It might be the steering box, but that would be an expensive guess... So I thought it would be a better idea to get some help from the board. So guys, please help. Someone must have had the same problem...

Steve Mac · 24th October 2009, 10:05

Unbalanced propshaft or faulty universal joint/propshaft coupling /guibo.

Change the "UJ" its the cheapest option

Also has the balancing been done on all four wheels??

davidoli · 24th October 2009, 10:25

I would certainly fit another set of standard fitment wheels to rule out any issues in that department .

D

Frits · 24th October 2009, 10:26

Yeah, we tried with different wheels allready.

Well, I thought about the guibo too, but my mechanic didn't think that would be the issue. Anyway, we'll have a look at it. I just checked, and we have it on stock, it's the same as E36/46 M3

Frits · 24th October 2009, 11:18

Allright, I just did another test drive, and I tried to let it do it again, and then push the throttle. Doesn't help, I probably just got lucky the first time.

Car is on the lift now. I checked the guibo, brand new...

Frits · 24th October 2009, 11:27

There is some play where the driveshaft goes into the diff. At least 1 mm...

raymondw · 24th October 2009, 12:49

Frits,

Check the center-mount from the driveshaft. On GD55450, the rubber around the bearing was torn; due too which the propellorshaft vibrated in its enclosure with similar complaints like 'your' M5T.

Furthermore, did you torque the bolts from the front-suspension under load ? (i.e the car standing on its own wheels on a four column lift)

Ratty · 24th October 2009, 14:40

Just a guess, but could the crankshaft harmonic balancer be *******? I know Faz had loads of trouble diagnosing a strange vibration (I think on Tonys old M5), and it turned out to be the balancer..

Testing to see if the word '*******' c-r-a-c-k-e-d gets censored again.... lol

It does lol.... must be a rude word these days

davidoli · 24th October 2009, 15:23

Sounds obvious , but are the wheel bearings all good ?

Like Raymond , I suspect that the control arms are the most likely cause as the dampers have been replaced recently ....... were all upper and lower control arms / bushes renewed ?

Saying that , we have recently had a couple of 7 series displaying similar issues and the problem was eventually resolved by taking a bit of the play out of the steering box on the hex bolt adjustment .

However , this would suggest that the steering box has wear and will , at some point , need rebuilding / renewal .

D

Frits · 24th October 2009, 20:20

Quote:

Originally Posted by raymondw

Frits,

Check the center-mount from the driveshaft. On GD55450, the rubber around the bearing was torn; due too which the propellorshaft vibrated in its enclosure with similar complaints like 'your' M5T.

Furthermore, did you torque the bolts from the front-suspension under load ? (i.e the car standing on its own wheels on a four column lift)

Well, next thing we'll do, is remove the exhaust, and have a look at the driveshaft, including the center bearing.

We noticed one engine mount (left side) is toast. Might not be the cause of the issue, but it certainly doesn't help to fix it.

Wheel bearings are OK.

Thanks for the input guys.