When you install a trans and you don’t get the torque converter installed all the way into the pump and then you install the transmission the end result will be damage to the torque converter and the pump.
Take a good look at the “hub” of the torque converter. This is the part that engages the pump and drives the pump. Notice that it has tabs. These tabs need to index properly into the pump.
Measure from the “pad” where the flywheel sits, immediately next to the torque converter stud, to the edge of the bell-housing where it mates to the engine. There should be about 1 inch. If it is smaller than this then rotate the converter and push it inwards. Sometimes this ends up being difficult. Sometimes it helps to sit the trans on its side with the pump facing upwards then rotating the converter, allowing gravity to push the converter in when its indexed properly.