I have an 84 EZGO 36v that I just converted from resistor to a controller. I got the controller setup out of a 90's model, complete controller, pot box, solenoid and F&R switch setup. I hooked everything up, bought brand new trojan batteries, bought brand new HD solenoid and changed all #6 cables to #4 cables ( all cables, not just the battery cables. I took the motor out had it checked and cleaned ( new brushes and brush holder) at a shop. After installing everything it ran good for a little while and then lost torgue. Lost it to where it will not climb over the edge of my concrete driveway 3" at most and to where you have to help it get started in the grass. Before it would almost spin the tires in the grass. I can unhook the battery cables overnight when I lose torque and hook them up the next day and have torque again. I have tested the pot box ( 0 to 5k smooth), Tested and load tested batteries ( 38.7v after full charge, still in break in period). I have taken the F&R switch off and cleaned ( Contacts looked great). The only thing left is the controller. Could this be the problem? Just trying to make sure I have checked all other possible problems before dropping $400 on a new controller. I forgot to mention that it runs fine once you get going just no torque.