4L80E, Tuning Help

[Jake's Performance]

Sounds like he has something off a bit on the tune for the WOT upshift but tell him to very carefully inspect the shift linkage/adjustment.

A 4L80E with the extra detent, using the normally supplied shifter lever on the trans, has the lever pulled back at such an extreme angle that shifting from 1-2 can be problematic. The cable is no longer pushing on the lever in the center of it's arc, it's pushing on it near the end and it makes for an almost straight line, so most of the force is going straight and not moving the lever.

Also ANY slop in the linkage creates problems. I've had to weld the pieces together that are normally bolted so they would have zero slop.

The valve body kit (if they used TransGo) has you restrict the feed to the low band. Many builders omit this step. Admittedly the method looks archaic but it does prevent harsh 2-1 shift.

I wouldn't shift it manually to low gear under decel until stopped.