99 z28, 3.73's 2800 converter, tci shift kit. Was playing with my Gtech the other day and made a run. Trans didn't shift 2-3. Hit the rev limiter and shut off fuel at 6200. 1-2 shift was perfect, around 5500rpm and nice and hard. Only tuning is with a hand held (FAST) and shift points are supposedly stock which is what I want. Motor is stock except for cold ari intake and lid. Even with problems and letting out of it around 1200 ft, it still went 13.25 @105, so it does run. Could this be caused by the shift kit? New to F bodies, so in the dark here.

 

It's most likely the mechanical timing between 2nd band release and 3rd clutch apply. Yes the shift kit alters the separator plate hole sizes which can cause this problem.
Could also be the 3-4 clutches going out, set up with too much clearance, etc.

 

thanks. Looks like when I get this taken care of It should be a nice high 12 second car.