88 240 rear end vibration

I've just noticed a new and slightly loud vibration/whine from my rear
end (88 240 sedan w/180,000 km) which is only noticeable above 80 km/h
and only when I am pressing/holding the gas pedal. As soon as I release
the gas, the whine/vibration goes away. The centre bearing & housing
was recently replaced in the tailshaft, as well as the tailshaft
bushing/seal/gasket. Anyone have any ideas what this noise could be?
Maybe an exhaust leak?

 

Have you checked the lube level in the differential yet? The symptoms sound
like it may be low.

Mike

 

Does the vibration happen specifically at the speed you mentioned, or
does it also happen whenever the engine is at a certain rpm?
(regardless of what gear the transmission is in) If so, and given the
age of your car, I would suspect the bushings in the rear end are bad,
namely the torque rod bushings. These bushings exert force on the car
whenever you are pressing the gas or pressing the brake. Does the
vibration go away when you get above a certain speed or rpm? If so,
that's a pretty good indicator that it's bushing related. The
vibration of the engine is being transferred to the body of the car and
the car is resonating with it at certain frequencies. If the vibration
does not go away above certain speeds/rpms but gets louder/changed
pitch then I would look more at the rear differential.

 

Thanks for your responses. The torque rod bushings were actually
changed last fall but none of the other rear end suspension bushings
were changed. I'm not sure what rpm's the engine is at when this noise
is present (no tach), but it seems to the worst at around 80 km/h. The
noise quiets down when I get up to 110-120 km/h, but it could also be
masked by the wind noise (which is much louder at that speed!). I will
be on the highway later this week and will double check this. Plus, I
will definitely also check the diff oil levels to make sure those are
good (I'm keeping my fingers crossed that everything is ok in the
differential!).

 

Sounds like the symptoms of bad trailing arm bushings to me. These are
the bushings directly below the rear axle.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)