If the truck moves slow or in a jerky motion you could have a problem with the encoder bearing in the traction motor or the wiring to the encoder bearing. The tracton motor encoder is part of the rear bearing. The motor must be disassembled to replace it. Block the drive wheels off of the ground. At the motor connector for the encoder wires, wire 33 and 13P should check 12v at the motor with the key on and seat switch closed. Back probe wires 103 and 104 at the motor while very slowly rotating the front wheels. Voltage should alternate between 11 and 0 volts. No voltage change or 11 or 0 all the time would indicate a bad encoder or wiring. These might not be the correct wire numbers.