First, it's an AUTOMATIC and you are asking a manual tranny question if you
are asking HOW2 shift it
Second, as others have asked, ask if you mean the TC (torque converter, a hydraulic
coupling...think clutch on a manual) lock up or using the shift lever to manually
shift through the gears (and lock out the higher gears)
Again, it's an AUTOMATIC and it has it's computer and software to do the shifting
for you
Then the TH button on the newer ones...engineered to increase the level of
computer management of the AUTOMATIC. Endless threads on 'what is the TH for',
'when to use TH', etc...to the point that even that manual button will be
removed to become AUTOMATIC with an increase in complexity of the computer
system (increase in cost too)
The 'lock up' in the TC is to remove the hydraulic coupling (inherently has a
10%-20% slippage...where the torque multiplication comes from and the losses
with that slippage...heat and lower MPG)
The other is with the shift mechanism. Manually shift the automatic into which
ever it will allow you to and that then locks out all of the higher gears...but
some times the computer will override that manually selected gear and shift
into a higher gear to protect the drive train...mainly the engine from over rev'ing
