I have a M8540 with 300 hours on it. The problem is a growling noise in the transmission/rear end area when the tractor is started. When I start the tractor in hot, warm or cold weather....doesn't matter, it often makes the noise, not all the time. It primarily does it when the shuttle shift is engaged in forward position and the transmission is in neutral. My local dealer is puzzled and been unable to give me a solid answer as to the cause. Any ideas would be greatly appreciated.