Hi; help needed. Have a 36v st marys cray forklift motor which was previously fitted to my hillman then direct coupled to the diff of my 89 subaru 4wd wagon. It was overgeared so I have fitted it to the gearbox. Formerly it would start on 24v. Now it will only start on 36v, then will run on 24 with no load. However, it will not start at all when in any gear and dor is reversed when running in neutral and dor alternates when attempting to take off in gear. Sparks and light smoke come from the motor . Put it in neutral and it will start in 36v. Brushes and commutator are accessible but as I have only worked on starter motors and old generators I thought it prudent to ask for help first. Any ideas?