Help w/Vibration please

[billy in slo]

still pretty new to the e34, have an e12 manual w/3.5, but the 90 535iA which I acquired in Dec. has a sort of harmonic vibration at hwy. speed. It is subtle and if I crank the stereo I don't really notice it but that is not an acceptable "fix". The PO replaced the tranny and driveshaft but I can not vouch for the work or integrity of the parts. So is it probably center support or guibo or are there other culprits within the tranny flywheel area? Thanks
billy

[Paul Shovestul]

My '90 535ia w/110k had a vibration at 40-42 mph and again at 60-65 mph. New trans mounts fixed it. The strange thing was vibration was always there after a cold start, but if you let car with hot engine sit for 30 minutes, vibration was gone. The trans mounts after many years of being cooked by exhaust heat had collapsed about 3/8". This caused the u-joint to run at a greater angle then normal, which in turn caused the u-joint to operate outside the "notch" that high mileage u-joints seem to develop. Letting the hot car sit for 30 minutes allowed the exhaust heat to warm up the front u-joint eliminating this "notch" which returned the next morning. Took 2 months to figure this cycle out. I don't think your car has a guibo. Mine has u-joints at trans and center bearing and a CV joint at differential. Can you determine if replacement driveshaft was new/rebuilt or just used? If it's new/rebuilt I doubt the center brg is bad....and it should have a warranty. It's possible center bearing wasn't preloaded. Check for evidence the trans mounts are new and/or were changed.

Paul Shovestul

[billy in slo]

10-4, thanks, my bad on the guibo, like I said, e12 guy till now :-)

[jplacson]

Just wondering... BMW Insp 2 turned up a "Propeller coupling" What is this? Is this the flex disc? Or center bearing? It wasn't expensive... I'm just wondering what this part is. Seems terms are different from shop to shop, so I just want to know what it was. Thanks!