Thank you Jim. Still a little puzzled because I removed the [electric]
motor and rotated the shift shaft manually. Between 4H and 4L the front
drive shaft never disengaged. Unfortunately I did not have the rear
wheels in the air so I couldn't tell for sure that the rear drive shaft
did not come free.

But you are suggesting that if I had the car in the air and rotated the
shift shaft manually, I would find the neutral position. If this is true,
I'm home free because a computer that can find that position is easy for
me. Lots of ways to do that.

Probably can't put the car in the air before weekend but I'll try then.

Thanks again - I'll keep you posted.