Gregory,

As I think on your issue I come back to a air supply problem. If it will engage and then when it is put into N for operation and that Is when it starts grinding, I wonder if you not loosing air pressure and or a bad supply line. A poor Air valve may also be an issue.

Could the module be canceling the signal and causing it to disengage and than engage. Best of luck and I will try to find the other info your looking for.

Jason R. Gohn
Technician/Shop Foreman
Greene County Highway Department
Springfield, Missouri, USA