Shift Point Question?

[crazychucky8]

Sorry guys, I know this may be a stupid question, but, I don't have experience in the tuning section. My brother-in-law has a silverado and wants to change his shift points with a hand held programmer. What is the difference and the effect of changing the shifts points negatively and or positively? Thanks for the help!

[tblu92]

It's rather confusing---But at part throttle operation--the shift is commanded by 1 parameter comprised of throttle position & MPH--
At wide open--it changes--The engine has to hit 2 parameters in order to command a shift--1 is MPH and the other is RPM---
A true full tuner can adjust all these tables correctly--however a handheld can only make small adjustments because if you adjust it too far it won't shift at all----a handheld when adding MPH to the shift points can only add it in the Part throttle area- at WOT you can set the shift RPM up higher but NOT the MPH parameter-- A handheld does not address BOTH parameter for a WOT shift--so on a heavily modded car or if adding or subtracting too many MPH at WOT you won't be able too or it may not shift at WOT---most handhelds have limiters to prevent you from going too far on a stock engine---where you can get into problems is using a handheld on a heavily modded engine which the handheld shifting program is not sufficient to correctly make it shift
Sorry to confuse you--this is the long answer--
The short answer---Add 3 PH to the 1-2 shift maybe 1 or 2 to the 2-3 and 3-4 shifts---set the shift RPM to 5600 in 1st---5400 in 2nd and 5200 in 3rd--- set the safety rev limiter to 6000----
IF you have larger than stock tires only make the changes in the 1-2 shift--You won't have enough power on a stock engine to set the WOT shift RPM higher and it will hang and hang forever at the 2-3 and 3-4 points before it shifts

PS: most improvements on an automatic are done with a real tune--I've seen cars and trucks gain 4-5 tenths in the 1/4 mile times without adding a single HP-trans tuning-for the street the best improvements are in tuning the DOWNSHIFT tables--these arent even addressed in a handheld--