diagnosing a drive train noise/vibration

[Happy Face]

my 72 'O2 has just had its tranny (4-speed) and diff replaced. I had it done at a local bimmer shop.

On the way home there was a new, scary vibration coming out of the drivetrain. It may be something that folks here have experienced.

basically it goes like this....when you are accelerating, and the car is feeling 'momentum' going forward, there is no noise, but when you let off a little on the gas, and you can feel the car's forward momentum lag a bit, there is a intense vibration or buzz (for lack of a better description) coming out from under the car. Again, when you press the accelerator, it seems to go away, when the car coasts or you let off on the forward motion, the buzz/vibration comes back. It seems to be coming from underneath, from the tranny/driveshaft/diff area.

Any ideas?

thanks

[pkbinplano]

(nt)

[PSloan]

I 2nd that - and MAYBE have a look at the tranny mount.

[BillWilliams]

take a look at the center bearing

[Happy Face]

thanks for the responses

with all the tranny, diff work that went on, there's a good chance that the guibo and center bearing took some abuse (on drive shaft, off drive shaft, etc..)

As I think about this, the center bearing could be the culprit..... oh boy, what fun

[Bill_Riblett]

Did they test drive the car after they did the work?

[Happy Face]

turns out the problem was a misaligned drive shaft. I got under there today and realigned the drive shaft and reattached the center bearing bracket. It was twisted/cockeyed. While I was at it I put the foam pad for the shifter back under the tranmission tunnel instead of up top (inside the car) where they had it. That helped to take some of the sloppiness out of the shifter. I had to take the drive shaft off to do it. While there I inspected the guibo and it looked fine.

Took the car around the block for a spin and the vibration is much reduced, but not entirely gone. I think the center bearing might need to be replaced. I'm regretting that particular exercise.

thanks for the helpful suggestions

[BillWilliams]

I can send you some pictures to help you when you are ready.