I have 92 z28 w/ 700r4. It is all stock as far as I can tell except for a toggle switch mounted next to the shift. I have been unable to determine what the switch is doing. In one position the RPMs drop about 500 and all is fine as long as I am at highway speed. Driving in the city there is a hesitation or somewhat of a lurch (spongy feel) to the car while in lower gears. If I flip the switch when going slower the car runs fine and the RPM pick up slightly. Any ideas based on this description. I don't think there is a shift kit installed because it shift nice and easy even at WOT.

 

Sounds like its a manual torq converter clutch lockup switch.

 

Aye. TCC switch.

 

I would be more concerned that having it this way may do some damage.i would consult the trans shop of your choice on this subject

 

Is a very commonly done mod ; especially if the car has had the computer removed ( carb swap )
there are better ways of doing it ,see
https://www.thirdgen.org/forums/carb...c-control.html

but manual switch is not a problem so long as you remember to turn it off at low revs or before coming to a stop (engine will stall)