When I put my 87 TII into gear and I accelerate, the whole engine/tranny seem to shake back and forth for a bit...then when I accelerate, everything cool, but as soon as I let go of the GAS, it feels like the engine/tranny moving again. Is this a Engine Mount or Tranny Mount problem? It happens or seems most noticeable at low rpms.

 

Another possibility may be a bad U-joint. That will happen at low speeds if it's the front U, and go away when you get over about 25-30 mph.

 

Eh man, that sounds about right!...damn, hope those aren't too expensive!