How is your engine braking?
Could be the one way bearing
Also there is some common noise when the engine brake is working going down a hill and braking, try putting it in 4 wheel drive and see if it's better or worse.
2010 Prowler XTZ 1000-
27" Grim Reaper Tires/Home Made Roof/Arctic Cat Mirror/Quadboss Folding Windshield w/ home made support bar/LED Tail-Brake lights//Venom 4000 lb Winch/Amsteel synthetic line/Home Made Doors/Custom Adjustable Seats/Custom Oh Crap bar for passenger/Tonneau Cover/Fat Max storage Box in bed
Tiger Tail Towing system