Sometimes when the accelerator is floored the transmission slips out of gear & the RPM's go through the roof. Any suggestions for a fix? 350 TPI engine.

 

Is this from a roll? At highway speeds? When downshifting? Upshifting?
The short answer is a burnt up clutch pack. But without hearing more of the details, I wouldn't be able to say 100%.

 

Downshifting is fine. Off the line shifting is Ok until shifting into drive & OD. At highway speeds, it instantly comes out of gear under hard acceleration. Thanks

 

tranny could be slipping or your low on tranny fluid also check your kick down cable from the motor to the tranny

 

It may not even be slipping. Our cars are setup to kick down into 3rd gear when you push the accelerator down more than 2/3 of the way. It doesn't matter if you're going over 100 mph, if you floor it, it'll kick out of OD and into 3rd gear, and believe me, at that speed the rpm's will hit the roof in 3rd! Ask me how I know. The Corvettes and cop cars are set up to stay in OD with the throttle floored, but not the f-bodies.