I have 3 20 series john deeres (6320, 6420, 7320) and they all do it. The pump load senses because of a broken o-ring in the back of the brake valve. I have replaced every one ( just the broken o-rings) and its almost an annual job on each tractor, o ring keeps going bad, the 20's were known for this. My question is there any update to remedy this? It looks like on JD parts there are no superseeding part numbers on the o ring or the little plunger/check valve the o ring goes on. Just wondering of anyone out there has heard/seen this and has found a solution? the 2 6000's don't overheat the hydraulic oil but the 7320 gets pretty hot from the pump always being pressured from the internal leak causing the pump to be in stroke.