Shift gears cuts off

I've never seen or heard of this before but I'll try and steer you in the right direction. 1st: With the hood open, have someone watch the engine to see how much it moves forward and backward when you go between Drive and Reverse & vice versa. (Parking brake on & foot on the brake.) If you're getting a lot of movement, there could be wiring that is losing connection or shorting against something as it moves. This can be caused by worn engine & Trans mounts. Wiring eventually starts to break apart after flexing too much for too long. Check your plug-in connectors to everything that could move-even the module wiring should be checked. 2nd: I would suspect that somehow your Neutral Safety Switch is shorting out the ignition. Normally this switch only provides a means for the system to complete the circuit, but more wires are contained within that unit that could cause a problem when shorted. Good luck:)