Suggestion for locating WHERE driveline noise is coming from

[SpencerM3]

Hey guys,

Looking for some help locating/diagnoising some rear driveline noise i've been having.

There is a medium pitched noise that starts around 40mph and gets a bit louder as I get up to highway speeds. Sounds like its coming from the rear, but hard to tell if its coming from one side or another.

So my question is, is there any way I can try to locate the noisy part without just randomly replacing things like bearings, joints, diffs, etc and hoping that it goes away? I did replace the diff fluid today. Old stuff looked like crap (thank you previous owner :roll: ) but the noise was still there.

Any ideas?

[f u z z]

Im having the same problem. But it happens only when its raining. Whenever my undecarrige gets wet i have this horrible rattlelting noise coming from my rear drivetrain, sounds like on the left side (drivers) but only when its wet. i thought it was a loose shock mount or somthign, but thats not it. i think its the gimbol (gymbol) i duno, ....

[SpencerM3]

Interesting that it would only happen when its wet.

Just to add to my description, the noise is a whining/buzzy type of noise.

[aaron_silva]

fuel pump?

Mine whines when I hit 80mph.

Aaron

[SpencerM3]

fuel pump?

Mine whines when I hit 80mph.

Aaron

Hmm...

Didn't even think about that. Does yours sounds like driveline noise? How did you diagnose it and determine it wasn't your driveline?

[aaron_silva]

The hum went away when I let off the gas, then continued when I started giving more gas.

Another thought could be your center support bearing. I am not sure what the sound like when they go bad, but that is a possibility.

Aaron

[SpencerM3]

The hum went away when I let off the gas, then continued when I started giving more gas.

Another thought could be your center support bearing. I am not sure what the sound like when they go bad, but that is a possibility.

Aaron

Thanks for the info. Noise defintely doesn't go away when I let off the gas.

Center support bearing is definetly a possibility.

[bimmerboy12]

whining

this seems to be a signature problem with E30's, nearly every one that I have ridden in makes this whining noise that increases with speed. My buddy spent hundreds of dollars having the dealer check out the rear diff, driveline, bearings, etc. and they could not find it. My 318 does it too. Another one of my friends claims the problem is a worn out speedo cable, a problem that originated in the 2002's. On a side note, my 88 325i cab does NOT make that noise and I DID replace my center support bearing... ;)

[Digitalwave]

Try changing your diff and tranny fluids if you haven't done them lately?

What the frickin hell is a gimbol?

[christophbmw]

The hum went away when I let off the gas, then continued when I started giving more gas.

Another thought could be your center support bearing. I am not sure what the sound like when they go bad, but that is a possibility.

Aaron

wouldnt the center support be more of a clunking noise? i know someone said this before but i i would replace my dif fluid and see if that works.

[fabianyee]

My car got whining sound too. some of the mechanics I consulted said it could be the bearings in the rear diff. It'll be an expensive job to replace those bearings in there...

[BimmerToad]

My 318is has a medium/low pitch wirl that starts at around 40mph and seems to be coming from the rear driver's side wheel. It's probably the wheel bearing, but I've heard that a bad flex disc (guibo) can cause drivetrain resonance in the rear shocks which can cause a similar noise.

But it's all good, since I'm switching to 5 lug from an E30 M3 w/ 50k mile parts, which probably have good bearings all around :)

[bimmerboy12]

The hum went away when I let off the gas, then continued when I started giving more gas.

Another thought could be your center support bearing. I am not sure what the sound like when they go bad, but that is a possibility.

Aaron

wouldnt the center support be more of a clunking noise? i know someone said this before but i i would replace my dif fluid and see if that works.

The center support bearing would make a clunking noise if the rubber holding the bearing is deteriorated. My 325i did that when I bought it none-running and I was towing it home. I'm thinking the whirring sound may be the bearing itself.

[SpencerM3]

As I mentioned in the original post, I did replace the diff fluid with some synthetic valvoline. Old stuff looked like hell but even with new fluid, the noise is still there.

I have a gut feeling that this is some sort of worn bearing. The question is, which one? Options are wheel bearing/s, diff bearings, center support bearing....

Also I jacked the rear of the car up and put it on stands. We rotated the driveline by hand and tried to hear anything out of the ordinary while laying under the car but didn't find anything that sounded out of the ordinary for a 17yr old car. Problem is, the noise doesn't really start til around 40mph, and I don't feel comfortable running the car on jack stands up through 2nd gear. Now only if I had a dyno at my house... 8)

[bimmerboy12]

did you try jacking up your car and seeing if the wheels move at all to test for wheel bearings, and try jiggling the driveshaft to see if its loose for that main bearing (forgot the technical term)? Maybe try for the center support too hell worth a try.