07 LBZ. No codes are set. All other gears work fine but no reverse. If I crank the truck, unplug large connector on rear of trans to force limp mode then it will go in reverse. Plug back in and once again no reverse. I’ve looked at wires and I visually see nothing wrong. Trans is an older build but doesn’t get beat on. Older guys truck jus cruises it most the time. I personally drove the truck about 60 miles without issue. When owner came to pick the truck up it hasn’t had reverse since. Any insight would be greatly appreciated
