So the rear end in my ct235 is quiet until it gets up to temp then it only gets whiny when it gets under a load. Even cutting the wheels and turning the tractor around will make it start whining but as long as I stay on flat level ground and no hills it’s quite as a mouse. I’ve had the tractor for approximately 1year and it’s always done it. It currently has 500hrs. And I did the 400 hr service myself with bobcat fluids and bobcat filters When I purchased it.Just curious if anyone else’s does this.. Thanks!!