Why, whats wrong with your TCM (failures are so rare, I would be looking elsewhere for faults)

the gears seem to be a bit strange as in often when you are for example driving along at 40 then you slightly press throttle nothing happens press a little harder and slight ecceleration press a little more and she drops down 2 gears then races off. or going up a hill when you can feel it needs to be in thrd and she's in fourth. i was told the tcu can be updated with new software which greatly improves the changing of gears i was also told the later models had a tcu with improved software. which i suppose should really have been my original question. is the ar tcu a later model with updated software and will it fit or have i been misled?