My tranny began mis-gearing today on the highway, reving high when it should have downshifted and then suddenly dropping gears...

Very similar to 60k miles ago when I FIRST had it replaced.

QUESTION: Will error codes be left in the computer? The reason for asking is that the nearest dealer is 70+ miles away from where I currently live, and I'm concerned that if they don't find an error code I'll waste a ton of time and be screwed.

I have a $0 deductible, 7 year 100k mile extended warranty.

Thanks,
G