On several occasions, the transmission has failed to engage when going from Park to Drive. Pull it to Drive and nothing, I mean nothing happens, yep, no click or buzz or anything.

GM cannot duplicate therefore it is not a problem. Once I pulled it into drive, nothing happened, then reset in park and went to drive again and it sent a total clunk thru the car to make it shudder.

Can't duplicate. Only happens when GM is not around.