I had to swap the case of my GSR trans because the threads blew out of the case for the passenger mount. Swapped everything over and put it back into the car yet I cannot get the car into 1st and second gear, it will go into every other gear no problem. Any idea what could be causing this? Transmission never had any issues prior to this

 

It's wise to test whether all gears work prior to reinstalling the housing.

You probably need to disassemble and check your work.

 

Ya I didn’t think of that too much because I only swapped out the outter half.

 

You do understand that you have to re-shim the main shaft to get the proper preload clearance when changing the transmission case right ?