[40cpe]

I've been thinking 'bout this. It might be unorthodox, but here goes. There is a cam on the reverse gear selector inside the shift cover that moves a rod backward that locks the OD section so it can reverse. If all else fails I would diagnose it this way: Put the main transmission in reverse, drain the gear oil and remove the side cover. Verify the reverse gear is indeed in reverse position. Then press the rod that goes into the OD section back into the case manually and hold it there. Have a second person start the engine and engage the clutch. If it still doesn't move, I don't see any more that can be done without removing the transmission and tearing it down. You will move the reverse gear back to neutral to get the side cover back on.