Truck not shifting upshifting out of first just super high rpms

You're tenacious; I'll give you that. Three posts! You've put a lot of money into parts and a lot of time and might have saved a lot of that by taking it to a trans pro instead. The truck's twenty years old and the trans is probably filthy. Before you changed fluid, did you flush the trans or check to see if it has a filter that's clogged? About all that's left is a faulty torque converter or a clutch pack at the planetary gears..... I'm guessing you got this truck free; no one would put all that money into a truck they paid three grand for.

What does the trans code say exactly. Like pressure control circuit A open shorted, torque converter slippage, over shift learn exceeded? 4L60E is a decent gear box if serviced and cared for, issues stem from one of three scenarios 1 abuse 2 lack of service, trans controller needing a software update. Suburban Yukon and Chevy in the 1500 group all suffer from ecm failure at some point. Impossible number of codes from 02 to reduced engine power are all tells ecm is needed beating an improper shifting trans is a killer.