I have a 7710 that we use for hauling sugar cane. The previous owner had removed the hitch as he had clearance issues with the trailer gooseneck and the rockshaft. I've removed the trailer and refitted the hitch so I can use it as a farm tractor during the slack season. When I refitted the hitch, I installed a new rockshaft position sensor, and tried to calibrate the HCU but it fails every time. I have checked all of the readings in the input addresses and they are in spec. The hitch works fine otherwise but there is no height limit control. One thing I have noticed is during the calibration, the hitch won't move a small amount as it should while turning the raise limit pot. It will only move using the slider. Any suggestions? Thanks.