Rebuilt 727 no forward or reverse.

I have a 1970 Challenger. 440 with a 727. I have been working on this project for 6 years. I rebuilt and installed the transmission around 4-5 years ago. The car is now running. The car is up on jack stands. When I put the car into gear it only moves the rear wheels when I rev the motor to approximately 3500-4000 rpms. I know on my Barracuda, when it is on stands and put into gear it moves the rear wheels at idle. Fluid level is good when checked in neutral. I removed the return line from the radiator cooler, started the motor, and fluid is pumping out of the cooler. I don't know if it is enough but it is moving. After letting the car idle for around 15 minutes this morning, I felt the transmission pan and it was not even warm. I read somewhere that it is possible to bolt the 727 to the motor without the torque converter fully engaged. Is this possible? Problem is I installed this 4-5 years ago and don't remember if the motor and 727 went together easy or if I had to crank them together with the bolts. Could there be something else wrong? Any ideas would be greatly appreciated. Thanks.
Author: bad1cuda