I have a 04 chevy tahoe 4x4 my 5.3 motor went out and bought a Gen 3 lq4 engine cause why not right haha..

I kept the same flexplate and notice I didn't have clearance for the starter so I change it with the a flat flex plate and work fine.

I bolt up everything but my transmission 4l60e went out, I grinded the tip of the drum assembly, what would I need to fix the problem. What could be the problem??? please help I'm new at these.

Note: at first i thought i didn't push the torque converter all the way so i bought another Trans with warranty and made sure I pushed it all the way in this time. but it still grinded the drum assembly its a ( 300mm)
sorry if I didn't explained myself good enough..

 

I don't quite follow what you are trying to explain, can you post pictures of where you ground the drum and a picture of the back of the crankshaft?

 

The "LQ4" covers a lot of years. Did you perhaps get a 1999 version with the "long" crank? That will not work with a 300mm LS-style 4L60E.