The Imperial website has a troubleshooting manual available for download. I’m a bad mechanic but I was able to follow it easily. One other thing to check, on the right side of the trans between the drain and fill plugs is another plug. Remove it and check that the bolt for the shift fork is tight. I believe you’ll need a 7/16 deep well socket. The m-6 is usually pretty bulletproof so it’s probably something minor. My problem was some bad wiring. Once I replaced it I’ve had no problems. Good luck.