TCC solenoid is dead, I'd bet money on it.
Is this all the time, or after the truck has warmed up, and then a stop, like coming off the freeway up to a light?
If the problem is consistent, and you can duplicate the results, pull the electrical connector from the drivers side of the transmission and try to make it stall how it normally does.
If the stalling goes away, the TCC solenoid is the problem. Easy fix, although I recommend a genuine GM TCC solenoid after having a bad experience with a "universal" aftermarket piece.