I can't comment on the diff thump that you
mention, but I also pursued a vibration, occurring
under load, which occasional seemed to disappear
at highway speed, which I finally pinned on my
tires. The tires were old, maybe 7 or 8 years, but
with very little use on them ( this is a British car
after all :-). They had developed flat spots and
when accelerating, with weight being transferred
to the rear of the car, the flat spotted front tires
caused the car to vibrate. New tires cured the
68 TR250, Cd8124L
Mitchel Seff wrote:
> OK, I am totally frustrated. I have been trying to hunt down a
> vibration at speed that seems to be intermittent.
> Recap----Last summer I broke a Diff mount in a local car show auto-X,
> pulled the rear , made the repair & boxed in the supports. All is good
> but now I noticed a vibration at speed (45-60mph ) . I find a worn hub
> bearing that's thumping & replace that. Vibration is mostly gone but
> is still noticeable . No low end knock, balanced drive shaft, all new
> U-joints & solid, very little diff (or trany ) whine at low speed,
> smooth acceleration to 50 , then a definite vibration comes in. Worse
> under load ,never terrible, but there. After driving at highway speed
> for a while some times it disappears. It's predictable like a tire
> imbalance but affected by load, yet it does not happen at low speeds.
> Could a diff side carrier bearing be bad? The diff has well over
> 100,000 miles on it. Could a trany bearing cause this. The
> transmission works perfectly.
> This morning I put the car on jack stands & tried to isolate the noise
> with a stethoscope. A steady thump seemed to be coming from the diff
> but then quieted down after about 5 min. When I turn the tire by hand
> I can feel a definite thump during each revolution. If it is the rear
> I question why the symptom only appears at speed.
> Any suggestions would be appreciated, I'm toasted.
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