Is it the tranny,the gru, or me?

[trucklover]

What kind of driving characteristics should I expect when driving a pmd 4:1 gru along with the stock 3 speed? The 3 speed ran fine until I installed the gru. I have one of those truck puller motors from gardentrucking and this thing seems as though it does not want to drive slow and steady. It makes my tranny make noise and then it gives me no movement, then speeds up quickly. I have a notched left stick throttle set up. Do I have to change my driving technique?