fails to upshift at full throttle

Went to pass a car so I pushed accelerator to the floor. The car downshifted fine, accelerated and when car reached redline and should have shifted to next higher gear, it went into a 'false neutral' instead (failed to go to next gear but it had already 'left' the gear it was in.) When I took my foot off the pedal, the car made the upshift with a 'bang!' sound that didn't sound good for the transmission.

Later, while climbing a mountain pass in Colorado, the same thing happened (gas pedal fully depressed, car reached shift point and then failed to make the upshift.) It finally did shift when I took my foot off the gas, but it did so with a 'bang' noise, just like before.

With so few miles on the car, we took it back to the dealer for repair. They test drove the car and were able to duplicate the problem. Yea! But they didn't know how to fix it. So they took a new Corolla off the lot and were able to duplicate the problem with that car, too. Based on that, they classified the problem as a 'characteristic of the vehicle' and stated they had no fix for the issue at that time.

Over the years, I have just learned that I can't "push the pedal to the metal" and expect the car to upshift properly. I now ease off the gas before reaching redline to help the car make the upshift. Its a nuisance and not normal, but that's just how it is with this particular year Corolla.