its a bit of both actually

 

Like Scott says, the pcm is told to change at lets say 5800rpm, the 35mph stored is the max speed the gear can go before changing.

 

See i thought that if you changed gears, the tune shifts at whatever RPM you have it set at. When you drive a manual you dont watch your speed and then shift...

 

It still will, but there is actually TWO things that need to happen for WOT upshifts...one, it needs to meet or exceed the MPH that is set in the WOT upshift parameter, and two, it must also meet or exceed the set RPM. If BOTH things do not happen, then it will not shift at WOT.

Like said, the speedo will definitely be off due to gear swap, and you'll also probably have TCC (torque converter clutch) issues with the lock/unlock acting weird.

On my 02 Silverado, I had shift points and RPM points dialed in very nicely, then scored a set of slightly shorter tires and for the two days or so before I reflashed the pcm with the correct tire height, it shifted fine, but acted a little funky on the highway and at higher cruise speeds...I'm going to say due to the different than tuned for RPM's/MPH's with the shorter tires.

Re'flashed with correct tire heights, it's back to shifting and locking normally.