When plowing with my 08 Sportsman 500 HO EFI I get on a slippery or rough surface and go to back up. There is a clunking noise coming from, I'm guessing, the front gearbox. Mostly in reverse, but also in forward, when stuck. (on a log) It never does it when there is traction to all four tires. I don't think the right front wheel spins when in 4WD. Can anyone please help me? Thank you so much in advance!