A. Bomb

I have had this truck (in sig) for 18 months or so. Always shifted slow/late 1-2. WOT would have it hang at 2600 RPM or so for half a second, then kick to 2nd.

All other shifts are fast like they should be. This transmission shifts firm, hard even, and crisply. Does not slip in any gear. No codes. Fluid recently changed and bands adjusted. Fluid looks perfect. Little to no trash in the fluid when I changed it after at least 25k miles. It is at the half-way point on the dipstick idling warm in neutral. Fluid is Castrol ATF +4

Trans was rebuild probably 50k miles ago before I got the truck. It has at the very least a billet converter and billet band apply levers, dont know what else.

Any suggestions? TPS seems to read/function right and was adjusted by me to be within spec last fall but I have not adjusted it since.

gorms

I tried tuning the shift kit I had through transgo, and it was near impossible to find a balance between shifting way too soon under light throttle and shifting too late under full throttle via the line pressure adjustment. I found the best fix was 3K rpm kit, so even at a stock shift point it makes power and shifted out around 27-2800 rpm. Also makes the rest of the shifts a little more fun too.

justme-

fwiw check the TV cable is moving free like it should. If it is hangin up and not returning as it should it will delay the 1-2 shift as you describe.
The pivot at the transmission can bind.