Unless you floored it the tranny wouldn't up shift going up a hill. If anything it would down shift. If you were in "4th" gear when it down shifted on you the auto tranny for early tibs are known for occasional rough shifts out of 4th. It causes the tranny to need replaced a lot sooner than normal. But it takes a while to do that. Mine has done it once or twice and I've had the car for a while.

It's possible that if the other owner never flushed the tranny that you doing it now would cause all the gunk built up to come lose. Which I believe at 60k miles isn't too bad for it. But I'm told if your tranny gets over 100k miles without a tranny flush that you should never do it because it will knock all the gunk lose and ruin your tranny.

 

Thanks for the reply.
I might have used upshift and downshift wrong. It was in a lower gear and going up the hill the rev was near 3500 and I wanted to see what would happen if I ease off on gas and let it go to a higher gear. It did go but with a nasty jerk.

I guess there is no point speculating on the tranny behavour. Just makes you loose sleep! Will a tranny cooler extend the life?

 

just buy a new tranny and be done with it. there really isnt a reason to sit and rack your brain about it. when in all reality you can get manual trannys for under 300 bucks. idk about the auto trannys but they really cant be much more then the manual and even if they were you can still get them for under 600