I have purchased a 2002 STX 450 Quadtrac tractor. The trans in 1st forward and 1 reverse is so jumpy and fast it is almost dangerous trying to back up to an implement or to back an implement into the shed. My dealership just came out and re-calibrated the trans, but it did not help much at all. I have a 2001 STX 375 quad and it is smooth as silk.....any ideas??????