I just picked it up today, and all was well. Dealer inspection showed no issues. Took it out for a spin with a friend, and I heard a loud *bang* during hard acceleration. The noise seemed to come from the right rear. Now the car rumbles loudly above 15-20 MPH, and the banging noise is reproduceable by shifting to reverse, backing up - *bang* - then shifting into drive and driving off - *bang*.

Any guesses on what I did by getting on the gas so hard? Only thing I can imagine (beyond my worse nightmare - screwed by the seller) is that a recent alignment left something in the suspension not tight enough.

Any ideas are appreciated.

 

get it back to were you got it from, bmws are floored to the ground on a regular, and that never happens, you must get it checked otherwise it may get worse.

Especiall when its clunking, or banging noises as you described.

Good luck..!!

 

Rear differential, wheel bearing?
Are your wheel nuts tight?

 

Good thought. I checked and they're all tight. If only it could've been that easy!

I'm not even driving the car now out of fear of doing damage. They're supposed to pick it up today. I'm really hoping they just left something loose when finishing up the alignment!

Any other ideas are welcome. I'm rather panicked over this!

I had turned off DSC for the first time when this problem started. Probably means nothing, but who knows...

 

Another point of data - if I step on the brake hard, and put it in drive or reverse, and give just a little gas, the sound repeats. For example, if I did it in reverse, to get the noise again I have to put it in drive, and vice versa.

Almost sounds like the drivetrain, but I'm not sure. Ideas?

 

At this point, I'm just providing data for those that might ever run into this.

Had an opportunity to look at the car under a lift, with transmission interaction. The right rear axle appears to have a problem, just to the wheel side of the CV joint. When the car is put in drive (or reverse), it literally slips the axle forward (or backward) when throttle is applied, instead of spinning the wheel. The result is a tremendously loud and frightening **thung** sound.

If only I'd had this car for a few months or something. This occurred the very day I acquired it. Bad luck? Who knows. I don't think this is something that could've been hidden by the seller, though.

A dealer now has the car for a warranty repair. Hopefully they don't decide its not covered.

 

Update...

The dealer has fixed the problem under warranty. It seems the mechanical aspects of the CV joint couldn't handle the fast start I requested of them and they fell apart. I took a look while the car was up on the dealer's lift. The CV boot was completely ripped, and the wheel would spin freely with minimal effort. While the wheel was spinning, the axle was stationary. Complete failure.

I was planning on taking the car on a long trip down into Mexico next month. Good thing it didn't happen there. Scary.

I hope nobody else ever has this happen to them. It wasn't a pleasant experience.

 

Glad it all worked out -- I must say that these cars should be able to handle a "fast start" so at least while you have a warranty, don't forget to have fun with the car...