Just changed tranny fluid & filter in 85 IROC with stock 700 r-4 with no shift kit and under 50,000 mi. Needs 8 qts to refill. I put in 6 qts of Amsoil Super shift, the rest Amsoil regular synthetic. tranny fluid. Due to winter, I have not driven it yet. What kind of shifts can I expect? Slightly firmer than stock? Too firm? I was especially interrested in firming up the 2-3 shift. They tend to be a little "soft" in these trannys. Comments?

 

It's probably going to be "harsher" rather than "firmer". The Super Shift only changes the way the clutch plates slip as a gear change occurs, not the way the gear change occurs. A shift kit is a better idea than the Super Shift for a street car.

I've got about that ratio of Super Shift to AMSOIL Dexron-type ATF in the TH400 in the '57, which also has a shift kit. I'm driving it this week because I'm doing a shift kit in the Camaro (it got involved - but that's another story). The shifts can be pretty wicked sometimes.