The transmission in a '86 voyager is not computer controlled. I assume that you have the 3-speed automatic and not a 5-speed manual. The van is not worth as much as a transmission cost to replace or fix.
The "Blue Book" private party resale value of a running, no mechanical problems '86 Voyager with AT and Air is $250-$300. Subtract some for any problems or worn out items. With a bad transmission, you may have to pay the junk yard to haul it away.