In case anyone else comes across this post with a similar problem, my '94 with AW-4 auto trans was doing the same thing, I could find all gears but not park. Additional symptom was lots of slop in the shifter when shifting into gear positions. If I held the shifter all the way forward, PARK would engage, but when I let go it would slip into REVERSE. The problem was the cable bracket on the transmission was loose, and let the cable act like it was out of adjustment. I used some thread sealant and 1/2" socket to tighten the bracket, now it goes into PARK and there is no slop in the shifter.