I have a slight problem that is making mowing relatively difficult on hills. I have a 34" Gravely walk behind, belt driven with pistol grip controls. I have both pistol grips adjusted to the same tension, but the right drive wheel tends to lock up more easily than the wheel on the left. The wheel slows down to a point, and then just locks up instead of slowing down further. This makes mowing on hills sloping up to the right difficult to do without slowing down considerably. Or when braking down hills, the wheel on the left slows down like it is supposed to, whereas the wheel on the right locks and drags on the ground. This is tearing up turf. I assume this is a simple adjustment, but I can't figure it out. Both grips are adjusted to the same tension, yet one is locking up more easily. Why is this?