What could cause a mild to moderate "thud" when accelerating from 1 to 2 gear on 1997 Acura TL

Front a stop position, a thud is heard from the right rear when accelerating quickly, only from 1 to 2 gear. Dose seem to be more noticeable the more quickly you accelerate. If you consciously accelerate slowly, there is no sound.

I've thought perhaps transmission, seems likely, but that is not where the sound is coming from. Any ideas?

Asked by for the 1997 Acura TL
poss trans or motor mounts