'81 240 clunks/vibrates on the highway

Has 280K, but had U-joints and carrier bearing replaced in the past. When
going down the highway either in 4th or OD, if I let off the gas and then hit
it, there's short buzz/vibration and/or a clunk that sounds like it's coming
from under the car between the seats, then it smooths out and drives normally.

Could this be a transmission mount at the cross-member? I had an '85 Camaro do
a similar thing (the clunk, not the vibration) and that's what it was. I
haven't been under it yet to see.

It needs a clutch, so I'll have it out anyway in a few days. Just wondered if
this part should be ordered in advance or if I can find one easily.
KennyH

Horsepower is cheaper than therapy.

 

Just a thought..could the clunk be something in the boot, like a loose tire
iron or jack ?

 

Just a thought..could the clunk be something in the boot, like a loose tire

No, sometimes it's a buzz, and it's driveline related. I don't know if the
overdrive unit is slipping or the differential is acting up.

It could even be loose rear suspension bushings allowing the driveshaft to move
too much.
KennyH

Horsepower is cheaper than therapy.