Has anyone changed the differential, and rear drive gear lube, in a 2017 Prowler 500? The owner's manual says the front differential holds 8.5 oz, which I was able to replace. The rear is supposed to hold 7.8 oz, but I was only able to get about 3.5 oz, and I drained it, and tried twice. Has anyone else had this issue? I don't want to burn the rear drive up.