Problem:

put car in reverse, give it some gas, pull the clutch and CLUNK...feels like the transmission just abruptly moved to the left.

put it in first, give it some gas, pull the clutch and CLUNK...feels like it just went back to where it is supposed to be.

It doesnt happen if i baby it forward and backward, only if i hit it a little hard. from the drivers seat, it sounds like its right below me. feels kinda like something coming out of joint and then going back in. driveshaft? trans mount? inside the t45?