I have a 1993 7.4 k2500 with the 4l80e in it.the problem is when I start it and drive it it shifts great and tc locks great then about 2-3 miles cruising about 55 the tc will unlock and not lock again till I turn the truck off for 20 sec then start it again then everything all over. If I keep driving it when it unlocks I'll be doing 55mph with almost 3000rpm. And if I keep driving like that code 39 tcc error will come up.what is this caused by and why when I restart the truck does it shift fine for the first few miles. I've changed the a&b solenoids tcc solenoid, pressure solenoid, the input &output speed sensors,cleaned the main trans plug,new tps and adjusted correctly ,good map sensor,and new brake switch.