Ok. I have a 1993 K3500 with the 7.4l and 4L80e trans. When I purchased the truck it had an issue with the trans. While just cruising in overdrive no matter speed, it would lock and unlock. My rpms would go up and down. Well, I decided to go underneath and take a look at the plug on the trans and found a wire that was missing the outer covering. So, since my truck is a 93 with the old style with the bolt in the middle of the plug, I went ahead and upgraded the internal and external harnesses along with the solenoids. Now, the truck will only shift into overdrive when the truck is cold for about a mile and then shifts back to 3rd. Needing help from anyone that has experienced this problem before. What would be causing this? The trans shifts very firm from 1-2 and 2-3 but once it sees any temp change in fluid it will not shift passed 3rd. I have ordered a valve body kit along with the tcc solenoid valve. Have yet to put it all in do to me wanting to get more information from here.