I was driving my 5Ton (M813) this weekend and had some problems with it. As I was driving it felt as if was slipping a gear and the entire truck would shake for a second. It felt as it if was coming from the rear of the truck. I check at the differential fluid levels and was was a bit low but not bad. Has anyone had a problem similiar to this. I asked some other friend and they suggested either the clutch slipping or maybe the gears in one of the pumpkins were going bad. HELP.