This T100 is 2WD, V6 and AT. The first concern is shifting from 2nd into 3rd won't occur until the operating temp. is halfway up to normal. (I usually warm it first). The second concern is that it won't shift into OD until over 52 MPH (aprox. 2600 RPM) and only if I let off the accelerator. This AT has been serviced 3 times and the truck has only 120,000 miles on it.
Any info as to what else effects the shifting times will be appreciated.

That's normal.