help needed please to diagnose vibration...

[JRKOUPE]

on my 1990 325i w/ 114k miles.

car has developed a mild/moderate vibration thru chassis at 80 mph. Not really felt thru st wheel much and she brakes fine from that speed w/ no increase in vibrations. Car has moslty new "chassis" parts EXCEPT for:


guibo
center support bearing
rt lca
tie rods


....other wise she's rock solid, tracks well, brakes well, corners well. Ill put new wheels/tires on over weekend to rule that out but what could it be?...Your help will prevent me from buying any of the above old parts needlessly..altho alll those items SHOULD be done! TIA

[Garageaholic]

it's either the guibo or center bearing.

if not , ur driveshaft is imbalanced, and the resonant frequency happens to have constructive interference at around 80mph.
I would look into that..

[JRKOUPE]

it's either the guibo or center bearing.

if not , ur driveshaft is imbalanced, and the resonant frequency happens to have constructive interference at around 80mph.
I would look into that..

Frank....sounds sensible.

I would hesitate about driveshaft being imbalanced though as car has been great since I've owned her and there has been no tampering/removal of shaft..... or any accidents. Is that something that can develop over time?.......I will look at /replace center bearing and guibo tho.......thanks

[Dave]

I would hesitate about driveshaft being imbalanced though as car has been great since I've owned her and there has been no tampering/removal of shaft..... or any accidents. Is that something that can develop over time?.......I will look at /replace center bearing and guibo tho.......thanks

Of the 4 on your list, I'd agree that it is more likley the CSB or guibo. The CA or Tie rod would more likely give you the shimmy in the steering wheel at times.

[Garageaholic]

True dave. i agree...

Although I have heard that after 20 years ( especially if living in hot summer and cold winter climates), that the expansion/contraction of the DS after that much time will yield a minor imbalance. But i've only heard that happen once, and i'm skeptical. I hope and think that that's not the problem.

[AdamF 88iS]

Check your wheel balances too.

[DaN]

When you order the guibo and support bearing, get the little rubber bushing that mounts in the center of the driveshaft at the trans.

If thats messed up, it allows the d/shaft to drift off center and vibrate at speed.

[Bimmerfanatik]

I had this same problem on my euro eta, albeit a bit less "mild" and a bit more SHAKE THE FUCK OUT OF ME :)

Anyways, I replaced the driveshaft with a low mileage good u-jointed one, threw on a new flex disc and csb, and hit the road. The MAJORITY of the shaking and vibrating was gone, but there was still some shake at 80-ish. I happened to drive straight to Pep Boys (only place open at 4 in the afternoon Sat to do wheels/tires) and had them mount and balance some tires onto a set of clean weaves I had. Turns out the "universal" ugly ass wheels I had were bent to shit, and far from hubcentric - woot.

In summary - replace the driveshaft stuff, and check your wheels - could be either or both...

[JRKOUPE]

shake

Im on it......


thanks!!!!