My 93 k1500 started downshifting an upshifting eraticly at 60 mph so I slowed down to 55 it stopped get up to 60 it starts again, I get off the highway an stop an take off it won't go into first it was stuck in second gear. Ran codes trans temp to high and an overspeed code,
So I replaced the sensor in the pan that tells the computer the temp, the truck shifts fine until warm an then gets stuck in 2nd about 5 miles down the road, I need advice to fix it. I think I may have bad pcm/ecu.

 

do you have an external cooler?

 

Whos tuning this for you?