Drivetrain 1991 lx 5.0 aod trans issue

I would check the TV cable first. It might need adjustment or possibly replacement. I currently have a Lentech valvebody in mine, but I'm sure adjustment is the same. My cable froze up/stuck over last winter and initially would not shift into OD at all (Lentech VB will lock out OD under WOT). I found a good used one and all good now.

The way I set mine this spring/summer was to unhook from the throttle arm and I moved the adjuster so that I had to pull the cable approximately 1/2" (from completely relaxed) before it could be snapped back into the throttle arm. This gave me a nice reasonable shift into OD. Originally I set it according to Lentech instruction manual and I could not get shift into OD below 55 mph and would downshift on deceleration at 40-45. Now it will shift into OD when I lift the throttle above 45 mph and not downshift on deceleration until 30-35, nice when you want to coast around through town.