FYI, a bent tranny output shaft on mine causing a vibration on acceleration
& cruise. Invariable got worse with each passing mile.. though probably
pretty rare (& probably related to either serious bottoming out or dropping
from a lift), something you might check for whenever u-joints are suspect,
or a rear seal is bad (a bent output shaft will ream the hell out of a rear
seal quickly). (Left un-spotted, this also rubbed the front yoke till it
was worthless and had to be replaced.) Soon as I noticed a pattern of
vibration, things got worse or started happening at different times. You
can check this by taking off the driveline, BLOCKING the wheels, and
putting it in gear with motor running, and CAREFULLY looking at the rear
output shaft as the engine runs. There's a machine hole drilled center in
the shaft, and you'll notice it moving in a circle if the shaft is bent.
It seems to me that, if your truck's vibration goes away with torgue
applied to the driveline, there might be a loose bolt/joint that is being
held fast when under direct torque from the engine w/ clutch engaged, but
wobbling when drag is counter-applied from the driveline to a disengaged
tranny/braking motor.(hey, it's a theory) Might also point to a driveshaft
in need of balancing? (If you can't find locally, TF output shafts, rear
seals, bearings, u-joints etc. are available from Universal Joint Sales in
Syracuse. Their number is 315-475-7241.)
Rain water that finds its way into a long-standing flat tire and is
unnoticed when it's re-inflated can work as a harmonic balancer up to a
certain speed, but then act as a few-pound centrifuge and cause some
serious vibration.
FWIW, My 55 TF sub REALLY doesn't like ~45-~53 MPH, even after new front
and rear bearings, rear seal, u-joints, front yoke, and a balanced
driveshaft. Rattle and hum.. one of those things I meant to put to the
group one of these days to see if anybody's had similar experiences and was
able to find anything to fix it.
>I am experiencing severe drivetrain vibration. This happens only when I
>let off the gas at freeway speeds and does not occur during acceleration.
>The vibe seems to come from the tranny area and on back.
>I suspect bad U-joint(s). Can anyone confirm these symptoms?
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