I just replace the motor in my Nissan truck and it was driving well I went down to the store when inside came back out and went to put it in reverse and it wouldn't go into any gear it's like it's stuck in neutral you can hear the motor it's running great I'll check the flywheel to torque converter the starter the shifter but can't find what would cause it. Can someone please help

will not go in reverse it is a 5 speed how much is it to fix it and do you have to ripe apart the tranny ? text me the answer at 570 874 9423