01 3/4T. A mild tune, likely less than 75/80HP. All stock, otherwise.
Truck will accelerate VERY well, from a stop, upshift to 2nd, stay in 2nd, at the governor stop, [3300+/-], for several seconds, then shift VERY hard, and continue to "git r done".
NE ideas as to what the cause/fix, [if any] is??