If we are talking about the same thing, It happens to mine every so often. If I am in high gear, and let off the gas with the intent of just slowing down or slowing to a stop, it looses the engine braking, feels like it goes into a free rolling state like it has slipped out of gear while sounding & feeling like the gears are grinding themselves up. If I step on the gas, everything engages and it goes back to normal. If I step on the brake and stop, the gears grind till the machine comes to a stop. I have reported it to my local dealer. They could not duplicate the situation but said they would make a note of it in my file in case it becomes a warranty issue. They thought I was experiencing axle slap.
It has never done this in low gear.
It has never done this in low gear.