Long story short...

the other day i got in my truck, started it, and when i started down the street, it was shifting really off and hard! I stopped the truck, turned it off, restarted it, and she shifted beautiful as always. I think something is going out on the truck.

now the longer story...

This Summer I Just took the truck on a 4100 mile journey from tennessee up the east coast to canada and back towing my camper. Truck performed perfectly. right after we got home, i noticed my speedo started reading incorrectly, saying i was doing "40" if is was idling or things like that. Anyway, I decided I would take the truck in and get a fluid change since i had just come from this long trip. Dropped the truck off at the transmission shop, 1 hour later the guy calls me and says "your transmission isnt shifting right, it needs to be rebuilt, i need 1700 dollars" I say, what??? i just drove over 4k miles without a problem. I go pick the truck up and its shifting perfectly.

fast forward to the first paragraph i typed.... it seems to me this could be some electronic thing about to go out. Why else would it shift perfectly all the time. then cut the truck off and on, then it shifts at the wrong time and very hard.

any ideas?
truck is 6.0 gas engine with 100k miles on it, and has the regular transmission, not the allison