Go down the list a bit and find my post titled: 1981 M46 OD Question - Follow-up. Check all the responses. There is good information there and tests that are easy to perform with a Volt-Ohm Meter, or just a continuity tester. With everyone's help, I think I was able to track down the cause of a similar problem on my 81. Turned out to be the button on the shifter I think. It seems like the main culprits on the manual transmission are the button on the shifter and its wiring, the fourth gear switch on the passenger side of the tranny, the solenoid on the bottom driver's side of the tranny, or the famous relay to the left of the glove box behind the dash. The autos are a little different. On my daughter's 86 240 it turned out to be the relay. There are people who know a lot about this on the board.
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Thanks to everyone for all the help given, Doug C. 81 242 Brick on Blocks, stock; 86 240, 129K, pictured in Rolling once, now has smashed left quarter panel thanks to the driver of an F150. Daughter safe in her Volvo.