Whats the secret to hooking up on the street or the track? If i gun it from a stand still, i will spin through 3rd gear. I know the same would happen at the track and I doubt the burn out pit would help much with these BFG's. So whats the secret....ease into it? From a roll of say 15mph or so, it will hook up and scream, pretty much throw you in the back seat, but anything slower and it will just spin like crazy.

4wd HI. Use it.

really?!?

I dont have the auto-trac like the 1/2 tons. I thought about a 4-hi launch but wasnt sure whether to run it the full 1/4 or try and revert back to 2-hi part way down the track. Close to 100mph even for 4-hi seems a little much. Is this pretty common?

okay, after a butt load of searching, seems like I am the only one "NOT" using 4hi to launch...LOL. It just sounded harsh to me for some reason to try that, i didnt think the tcase and cv's could handle all that. I desperately need a way to keep these tires from spinning though, cant wait to give this a try.

okay, after a butt load of searching, seems like I am the only one "NOT" using 4hi to launch...LOL. It just sounded harsh to me for some reason to try that, i didnt think the tcase and cv's could handle all that. I desperately need a way to keep these tires from spinning though, cant wait to give this a try.

Think you will like it. Most of us Autotrack guys do switch back to 2wd at some point during the run but I have made several runs 4wd all the way. I do get some vibration at the end of the pulls. Even in switching to 2wd I think the front diff remains locked the transfer case just doesn't transfer power to the front.

okay, thanks. i did a dyno 1/4 mile and it ran high 13's, but i dont believe that to be very accurate. I do believe i am capable of mid 14's though with this truck cause stock 8.1's are running high 15's/low 16's, its just going to come down to hooking up.

Don't even think about bringing it up against the converter. I just sit there idling, release the brake, and "ease" on the throttle as much as the tires will take. If I power brake it against the converter it will "re-pave" the entire 1/4 mile, and even "flat footing" it from a stop will kill the tires. I have a lot less power, but have gotten pretty good at bringing it off. I'm sure with a good set of tires I could knock 3-5 tenths off of my E.T. You also might want to dry deflating the tires down to around 25lbs or so....maybe less. Fool around with tire pressure while you're at the track, but I'd run them fully inflated for daily driving.

So you "dont" launch in 4hi? I dont plan on power braking, but i figured a 4hi launch should keep the spinning (if any) down to a minimum.

Yeah, I know most people are leaving in 4HI, and I've been in a 14.4x Duramax truck when leaving like that...and it was sweet to say the least. My problem leaving in 4hi is I don't have 4wd...so I gotta peddle it out. :devil:

So your going to let something as simple as "not having 4wd" stop you from launching in 4hi? Funny, i didnt take you as being a quitter..... :jest:

:bang: I do what I can. Actually, there are about 2 days each year when I wish that I would have gotten 4wd....but for the other 363 days, I prefer 2wd. Going to the track Sunday? :devil:

i think so..... :drive:

not sure what time yet, but probably befor 12.

did some fartin around today in 4hi. I might just put it in 4hi everytime i stop at a red light....LMAO. Talk about torquey, my God, i thought it was fun spinning. Hooking is waaaayyy better than spinning. I cant believe i never tried that before, damn it feels good to punch it and just launch out with no spin!

I was wondering the same thing LINDA, i was told to leave it in 4 HI the whole down the track, but like k y said, you can feel a little vibration from the front end, i dont want to tare any thing up, but also want the best launch possible. ALSO, my friend T.J. taught me to come to a stop, shift in to nuetral, rev the motor a little and push the break hard to the floor, This helps your breaks hold better, then he said to start off in low 1 and manually go from there to drive after you launch. its spose to give you a better engagement of 1st gear in your tranny and after you launch in 1st you can actually shift into drive or o/d. Just a tip from your old uncle Eric. :jest:

did some fartin around today in 4hi. I might just put it in 4hi everytime i stop at a red light....LMAO. Talk about torquey, my God, i thought it was fun spinning. Hooking is waaaayyy better than spinning. I cant believe i never tried that before, damn it feels good to punch it and just launch out with no spin!

Now as Tim eluded to. Work on getting the launch down pat. Ty Shuffle- drop it to neutral and rev it while pressing the brake, let it idle back down the go back to drive. This will give you considerable more braking power. Now stall it as high as you can, probably around 1600 rpm with the factory stall converter. Let off the brake and mash it at the same time. HANG ON! Look at the picture in my sig. Truck is twisted and front end lifted to the end of suspension travel. Just a smidge of front wheel spin. Get it down pat and there are very few vehicles on the road that will keep up stop light to stop light.

That is one sweet ass launch Roger!

That is one sweet ass launch Roger!

Hey thanks, I actually need to work on my suspension. You want all that rear end loading in a 2wd launch. Not so good in 4wd. All that lift is wasted torque that could be used for forward motion. Rear leaf spring clamps, loosening the front torsion bars to set the front down a bit. Possibly a set of stiffer shocks. At least that is what I am gonna try this year.

well, my reaction times sucked. It was very busy and I only got a few runs, but each time i kept getting a little nervous. I think overall they are pretty good times for a 7000lb+ truck. I didnt try the rev and mash it option this time because i was still just a little worried about making the entire run in 4hi. Now that i have done it and the butterflies are wearing off, i know i can get this truck close to 13's. We still need to do a little more tuning, better reaction time, and if i rev up and mash it..... i think i can get darn close to 13's. Do the 60' times and other points on there (other than the reaction time :cry: ) look pretty consistant? Anything jump out at you? Good news is there was absolutely no vibration in the entire run, so next time its no holds barred.

EDIT:
Also, if i could get the shift points changed on this Allison trany, i think it would help alot too. The thing doesnt rev up much at all when shifting. Cant wait till someone has the codes to change the Allison trany's. Almost like i need to manually shift this thing, but i didnt have enough time to try everything i wanted to.

http://www.pasadenatownhall.com/picts/file0044.jpg