[s-cars] WTB - Rear Diff

[chris chambers]

Eric,

Couldn't you drop the driveshaft and run the car on a lift/jack stands
with no power to the rear diff...if no vibration is present then
continue to investigate as the source. If the vibration persists then
that would indicate that it's not the rear diff...right?


Chris


--- Eric Renneisen <racingiron at comcast.net> wrote:

> > 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
> 
> 
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