My 94 Z28 with auto o/d and about 89,000 miles seems to shudder or gear hunt at about 55+ mph, only after it’s been warmed up. I have to feather the throttle to get it to sort of calm down. It’sa little distressing to be out on a nice summer day and go to pass a semi only to have it hesitate and have to back off and fall back in line!

 

Sounds like you may describing torque converter lockup shudder. If that's what you are getting, then use this stuff, it really works: https://www.lubegard.com/products/isf/

 

Thanks I will check it out!

 

So I gave it a try, and drove about 10 miles and I think it helped! Thanks for the suggestion!

 

Awesome, glad to hear that.