Help... Rumbling Noise Coming from Rear??

[konabimmer]

My car (1993 325is w/ 110k) is making a loud rumbling noise during acceleration (seems to be coming from the rear). It's usually loudest at about 30-40 MPH. Although it starts sooner than that. Also, it only happens during acceleration.

I recently changed both the tranny fluid, as well as the rear diff fluid. Both looked great! Could the diff be fried? No metal shavings in the rear diff old oil though. Also, just put on a brand new OEM muffler, so its not that.

I've read numerous posts about bad wheel bearings.....If it were that, wouldn't it happen if my foot was on and off the gas? Also, it doesn't get worse turning one way or the other. Any known problems w/ the drivetrain? Broken mount? Wouldn't it vibrate more? I am boggled......Maybe someone can help me out? Thanks.

[SQ Bimmer]

Sounds like a wheel bearing. Lift a wheel up off the ground and wiggle your wheel to see if you get any play in the wheel. if you do its the bearing. If not, then you can have a bearing problem in the future, and until you get play in the wheel I wouldnt worry about it too much.

Also, is your gas mileage worse than normal? When i replaced my bad bearing at 170ish k miles, I got an extra 5-6 mpg...

edit: Worry about it ASAP if it is NOT the bearing... Shoulda added that part! lol

[Boolabear]

Check you bearings. I had the same issues and had the bearing replaced. Good to go now!

[328iBursche]

I think it's a drivetrain problem if you feel vibrations while this is occurring. Wheel bearings seem an obvious problem, and this doesn't sound obvious--but what do I know--I;ve not yet had a wheel bearing go bad on my bimmer. If it's me, I get it checked out and get ready to pay...hopefully not much
SO, BUMP!

[konabimmer]

Thanks to everyone that responded. It turns out it was the driveshaft. I guess after 110k it had enough. Usually I do all repairs myself, but this one is just way too hard w/o a rack. Took it to the stealer (Don't go there too often nowadays), and made my donation. Part was like $650, and labor $300. They discounted that though. Total w/ tax out the door, $935. I really havn't pumped too much cash into this car over the years, so I guess I was do. Cars been great for over 10 yrs, not including this. I am just praying the tranny or A/C doesn't go out(Although they have been working fine w/o any problems at all). Thanks.