ok guys need some help here need feed back on this wondering if something is wrong or is it normal ok here i go, i got a 6.2L denali with LTs, Intake, 3'' exhaust and a VVT small cam few months back on barrowed 17s with Drags i ran 12.89 @ 107.3 mph now with 18'' light weight wheels on all 4, Drags 305/45/18s on rear and when i launch it stalls and feels like its thinking too much and when 2nd kicks in same thing feels like it freezes for mini sec and my best time was a 13.21 @ 105.7mph and my 2 run it died *** soon as 2nd came in!!!!!!!! whats going on? could it be i need a Stall? drive normal on the street, HELP!!!!!!!!!!!!!!!!!!!!!!!!! and on 20s it ran 13.22 @ 104 whats the deal?

 

Almost seems like its in the tune..

 

Tune and maybe the change in tire size

 

Damn that's what I was afraid of a retune

 

I think that since the taller wheels/tires will effectively give you a higher gear ratio, you are dropping down under the power band. I guess a stall would fix that, or lower gears. I know that when I ran my cammed car on DRs with the stock gears, it would bog down at launch and feel like there was a delay before getting any power. The tires were sticking and dropping the RPMs below the cam's power band. Lower gears helped a lot.

 

Autos have to meet mph and rpm requirements to execute a shift. If you are shifting at 6300 on your 20's and these drs are shorter then those mph settings are likely causing it to over rev before the shift. Prolly needs a tune for what tire height u run at the track to shift on the spot.

 

Thanks guys for the info getting it retuned as of now with a new setup too

 

Check the fluid level in the trans. The 6l80e in my g8 did something very similar to what your describing on launch when it was a quart low... felt like it was coming out in 2nd then down shifting at the 60 (ish) foot mark. it would only do it with the DRs and not with street tires. Might be worth looking into if the retune doesnt cure the problem. I know it sounds dumb but the extra quart of fluid solved the problem and my 60s went from 2.0s to 1.8s

 

Sounds like you are enjoying the downfalls of the huge ratio difference between 1st and 2nd gear. The ratios 1-2 are wider than even the 4l60e/65e/70e.

Performance TC will help.

peace
Hog

 

I'm pretty sure he has the 6L80 or 6L90. Their 1-2 shift is NICE!