I'm having a problem with my 88 silverado at normal shifting.

Long story short, I bought this truck with a ls1 and a 98 pcm but it was not running good at wot so i decide to repin the pcm to a 2001, after the repin i took it for a drive and the tranny gave out (4l60). Took the tranny to get it fix and install it back 4 months later.

So now at part throttle it shifts good but after driving it for a while it starts holding the gears to long, but if i stop and re write the tune and drive it back it sifts good for another 10 minutes and then she starts holding on the gears.

Now i don't know if its the tranny or smething went wrong when i repin the pcm because on my scanner it does not show me the engine tempeture or tranny tempeture and it reads way off from the truck speedometer to my scanner.

What do you guys think it can be?
I was thinking on getting me another harness i dont think it can be the tranny going bad.

 

The fact that it works fine for 10 minutes after you reflash it leads me to believe it's in your tune. Try disabling the learn feature in the transmission tables.

 

Where are does tables at? Im using hptuners