I've owned this car for a little over a year now, and it's always done this. This is my 3rd 3rd-gen, all of which have been 700r4's and none of the others did this. It's an 85 iroc 305 tpi..

If I'm going around 70 and put the gas all the way down.. it wont shift.. it will just keep going until redline (which I don't do).. the only way to prevent this and actually have it shift is to let go of the gas a little bit, then it goes.. but if I gun it again then it downshifts/redlines. I've set my tv cable properly, all the other shift points are spot on. I have non stock rear tires which are bigger, but I doubt that is causing the issue.

The previous owner replaced the transmission (he sold the car about 50k miles after the new trans was put it), but it's still a 700r4.. he said it had a Corvette servo.. would that cause this?

Any help is highly appreciated, I thank you for your time.

 

This will fix it.

 

Corvette 700R4 and 4L60 will stay in 4th at WOT, all others down shift to 3rd. You can have yours built with Corvette internals so that it stays in 4th at WOT. My 88 will downshift to 3rd at WOT then shift into 4th at 85 to 90mph.

 

Was this done so the Corvette would be rated at a higher top speed than the Camaro? I just don't see a purpose for it. It's slightly annoying.. though I guess it's a good thing that I can't go faster than 100mph (>.>)

Thank you Morgsie I'll order that part when I get the chance, and thank you Camarorookie for giving me some insight.

 

Many f-body's also up shift and stay in 4th when floored. So it isn't a Corvette thing only. And yes, it is annoying. Set the speed limiter to 255 in the ECM and fixing the up shift problem increases the fun factor quite a bit.

RBob.

 

My Caprice 9C1 (cop car) shifts into 4th @ WOT as well. You can mod your 3/4 shift sleeve with a tap and some set screws. Try emailing Dana @ Probuilt he should be able to send you the instructions. I have them somewhere, if I find them I will post them. Will save you some money vs the Transgo one.