The engine/motor mount that gets the most stress is the right one. When the engine torques from loading, it wants to tilt to the left, compressing the left mount and pulling up on the right mount.

Test by putting your hand around the oil filter to see what clearance there is between the filter and the mount below it. Last one I had fail the filter was actually resting on the mount. Drat, made an even oil change into a late-night ending job. Had a mount in stock.

So test there. Also have your hand on the shift knob when the car upshifts under heavier-than-usual pedal. Feel for side-to-side movement in the handle. Do the same when slowing with car in gear. Won't be much movement, as the shift linkage sorta isolates the tranny from the knob.

You might also check the center drive shaft bearing. If that tread piece wrapped the drive shaft for a while, shaft balance gets real bad.

Good Luck,

Bob

:>)