[Efthreeoh]

Soooo.... THAT didn't work.

New bearings and new left halfshaft (the original one wasn't bad other than rust and ahem, munged-up threads...), but the vibration I was chasing is now even worse!

So I'm thinking the diff decided to go on to better pastures. I took the car to a local trans/diff shop (domestic mostly) and they thought it wasn't a diff issue... hummmm. They were thinking a driveshaft problem. The guibo and center bearing I replaced at 250,000, so I doubt it is either of them. The shop thought possibly the centering pin (going into the trans yoke) is out of round. My idea was to pull the diff an have them rebuild it (maybe install a limited slip unit...), which is why I contacted them. They are not a BMW shop by any stretch, but diffs are diffs...

So I'll pull the driveshaft and inspect it, but I'm confident it's not the issue. The vibration I'm chasing is only on deceleration. It's so bad that it literally vibrates the rear door panels and seat surround. Upon acceleration the drivetrain is smooth as silk. Trans shifts fine and no noise at speed and throttle applied. Makes the vibration whether in neutral or in gear. Clutch and flywheel are new as of 293,000.

I'm stumped. Any insight from anyone is welcomed.