this started out as a little vibration while backing up .. and now its gotten so bad i cant release the clutch while backing up. the problem is when i start to disengage the cluth and start to reverse the motor starts jumping like crazy as if it had no tranny mount or no mounts at all.the entire car shakes and you hear the motor just banging up and down it feels like it just gonna break off i check all the mounts are fine i had poilyurythane inserts everything is on there tight. i checked the cross member all seems fine i even put a jack to the motor to see if it lifts but it wont move. i also tryed pulling the ebreak up and putting it in reverse but the motor will barely move at all it only does it when the car starts to reverse it even worse if im on a hill or bump i literally need to get people to help push it back. motor will also do this if i down shift and let the rpm drop.. i cant figure this out.. i dont think its the tranny..any one got any ideas????