Hi there. When I press r?he reverse pedal on my John Deere 955, it begins to move, but when the load increases (backing up a hill or over a step) it's like it jumps out of gear, stops and you hear gears grinding against each other. It will driver forward OK, unti you realease the pedal. Instead of slowing down, it's also like it jumps out of gear, it contnues to roll as if you've pushed in the clutch and you also hear the gears grind. It al ost seems like something is free-wheeling in one direction, but not the other. Any help would be appreciated. Thanks!