[s-cars] WTB - Rear Diff

[Eric Renneisen]

> Most obvious best guess is a bent wheel, but "maddening" 
> assumes you have ruled this out. 

I started with that thought about a year ago.  I do have at least one
bent Bolero, but the vibes are present with three other sets of wheels.
FYI, an S4 looks really strange with urq Ronals!

> My own personal best guess then (and ICB wrong,once was) 
> is some bushing around the differential and not the diff 
> itself. My own similar maddening vibration was bad 
> bushings front of diff in the sub frame cross member 
> where diff attaches in the front. 

I did have a bad one of those and replaced them both.  I thought for
sure this was it (as I've thought about the dozens of other bad parts I
replaced).  It cured a clunk I had during harsh weight transfer moments,
but vibes are still there.

Basically, I've got a speed-dependent vibration (40 and 80 mph) that's
independent of gear selected (even neutral) and power application.  I'm
convinced it's a rotational imbalance somewhere, but it's proven
impossible to isolate, even when running the driveline up to speed on
the lift--I can see/feel the car vibrate, but not the source.  I've
swapped wheels, all driveshafts, two transmissions... not to mention all
the bushings and mounts.  One final clue is that I noticed the effect is
somewhat more pronounced with a full tank of fuel.  The diff seems
normal (no bearing wobble or strange noises) but I'm at the end of my
rope.  If this doesn't do it, I'm buying another one and breaking this
one for parts.

Thanks for the thoughts.

Eric R.
'86 urq
'93 urS