Author Topic: diagnose vibration (Read 2831 times)

doitover · « **on:** January 31, 2011, 08:55:02 AM »

I have a 1991 318is that has been idle for 8 months or so. Now that it is back on the road it has a wicked vibration that really kicks in around 50 to 55 mph.
It is independent of engine speed.

I would say it is due to the tires having flat spotted but the vibration smooths out considerably above 55. It is still there but not like you would expect for flat spotted tires.

Any ideas?

Thanks,

doitover · « **Reply #1 on:** January 31, 2011, 10:26:56 AM »

I think I've answered by own question on this. From what I've read it sounds like the driveshaft. Anyone have experience with

Driveshaft Specialist of Texas?

http://www.driveshaftspecialist.com

Thanks,

DesktopDave · « **Reply #2 on:** January 31, 2011, 05:30:29 PM »

I hope you're on the right track. An unbalanced driveshaft would shake in all gears at roughly the same RPM though, I'd figure. I'd guess front CABs, balljoints, bent rim, etc.

I have no experience with a drive shaft company, but I've heard good things about what they can do for an unbalanced one.

doitover · « **Reply #3 on:** January 31, 2011, 07:23:31 PM »

I hope I'm right too, I have all the parts ordered. Actually the drive shaft and back are the parts of the drive train that are RPM independent.

As far as I can tell, the rest of the rubber on the car is still in good shape. I think the previous owners (or more probably the one before that, GRM) at some point changed about everything out. I do have a rear wheel bearing on it's way out but the vibration doesn't seem to be coming from there.

doitover · « **Reply #4 on:** February 04, 2011, 09:39:33 AM »

Turns out I was wrong, at least partially.

The tires have gotten out of round. The really bad news is that one of the rims is bent. I really like the BBS's that are on the car, it may be a challenge to find a good replacement.