Need help. Setting up new gear set 742 case

Hey everyone. I'm attempting to change the ring and pinion set in a 742 case. Everything was looking good until I went to torque pinion nut to 240lbs and it all locks up. I reused the shims from the gear set I removed hoping it would get me close. The shim in between the pinion gear and aft bearing and a smaller shim on the top of the pinion. Do I need another smaller shim up top? Can someone tell me what I did wrong? Thanks