transmission trouble

Ok, whenever I take off from a dead stop and give the jeep too much gas, the transmission shutters. If I slowly accelerate, I don't have this problem. I am not sure if the transmission is slipping or if the torque converter is low. I just did an engine swap so I was thinking that the torque converter lost too much fluid. Is there any way to test what is wrong? Btw, I had the entire drivetrain out of the jeep. It only does it in first gear and after that it seems to drive fine.

tranny mount? motor mounts good? i had a 94 with a bad tranny mount and it kept rapidly banging the floor

it feels like it is slipping though. If i am light on the gas is doesn't slip. motor mounts are new

i just started having this problem too. if im stopped at a red light and then it goes green, when i am more aggressive it will will studder or slip, but if i go smooth it wont do this.