Recently acquired a JD X320 with 48" deck. The tractor creeps forward when returning to neutral from going forward but is fine when returning from reverse. Troubleshooting in manual states linkage out of adjustment but cannot find any instructions on how to adjust. I don't have a service manual so I'm not sure what direction to move the adjustment rod. I also have an X570 to use if I need to take it back to the dealer but I don't want to pay for a service that seems to be simple. Any suggestions.