Help with limp mode issue

[Mikeysev91]

I own a 1991 gmc 2500 454/4L80e truck with 37k miles. I’ve recently run into issues with the truck going into limp mode every time I drive it. Essentially what happens is it will start and drive around fine(other than hard shifts) and have all gears for the first 15-20 minutes of driving. As soon as I come to a stop after that timeframe I will get the CEL illuminated and the truck will be in limp mode with codes; 

24. VSS Signal 

73. Trans Temp 

85. PROM Read fail 

87. PROM 

 

         I’ve already investigated the pass through and it was leaking. I’ve cleaned it out and tried with no difference, from the bottom of the truck the wiring looks pretty good. At this rate I don’t know where to go in terms of diag, wondering if anyone else has seen this issue? , also any suggestions are more than welcome