I recently bought a 1990 Iroc Z convertible with the 5.0, 4 speed automatic and 2:73 rear end. The transmission shifts up and down a lot when it's in overdrive, like going up inclines or just letting off of the gas. I found that when going up a hill I might as well shift into drive before it lugs down and then shifts. Does it hurt it to shift by itself so much? Is all this shifting normal for this car? I realize that the high gearing is probably why it wants to shift so much. It doesn't seem to have much power in overdrive but that's probably because of the 305 and high gearing too. It does get great gas mileage though!

It's in great shape with 50m miles. I'm looking forward to spring weather for some top down cruising. Thanks for your input.

 

i don't know.... i had a 305 tbi (170hp) w/ the 700r4 auto and 2.73 rear end, and it would just about climb a tree before it shifted back into drive... are you sure your not feeling the converter lock and unlock... sometimes that can feel like a shift...

next time it does it reach down and pull the shifter back into drive and see if it down shifts... if it does then it isn't your tranny shifting it is your tc unlocking and as far as i know will be fine...

let us know

 

It is not good to let it cycle like that. When you approach a hill back shift it to 3rd so it won't go back and forth between 3rd & 4th. Better to have the engine wind up a little, than let it go back and forth between two gears. Around town keep it in 3rd, instead of it looking for 4th and then constantly going back to 3rd. This is one of the reasons the 2-4 band wears out prematurely.

 

Yes, I guess it is the convertor. I remember when it felt like it shifted down while I was going up a hill and I put it into drive and I felt it downshift. I had been told before when driving another vehicle, that has that transmission, to put it in drive when it is lugging down.
So, is the convertor or transmission hurt by this locking and unlocking?
Thanks

 

that I don't know....
I would imagine that it may wear out the converter over time.... but how much time that may take, I have no idea... It may be fine for it, I really dunno....
We will have to rely on someone else on this one....

Fella's??? or ladies as the case may be......