Competition Drag Racing. Shift from 4 to 2wd????

[John Dishong]

Hi Folks,

Been drag racing for a good while and wnat to get my top speed up. I have the launch in 4wd (auto) down pretty good. I wanted to know if anyone shift to 2 wd mid track to get the top speed up. I know that the Duramax can do it but I just don't know what will happen if I try to pop it out when I hit third under load.

Any thoughts or experience??

Thanks

John (Piers' Blue Truck from BD days)

 

[paulb]

Hi Folks,

Been drag racing for a good while and wnat to get my top speed up. I have the launch in 4wd (auto) down pretty good. I wanted to know if anyone shift to 2 wd mid track to get the top speed up. I know that the Duramax can do it but I just don't know what will happen if I try to pop it out when I hit third under load.

Any thoughts or experience??

Thanks

John (Piers' Blue Truck from BD days)

I've gotten in a habit of shifting it out of 4wd at the 1/8. Doesn't seem to make that much difference it ET or mph, but it sure does help making those sharp turns getting off the track...

 

[KLockliear]

With the auto trucks, I shift to 2HI after the 1-2 shift. On the manuals, you don't have time until 4th gear.

 

[BigDan]

Yes it will help out ALOT..... Just recently it cost me 3/10th's on my ET and 4 MPH.

 

[JR2]

I have just raced once and I did not do it. I did not think the truck would shift untill you lifted off the throttle so I did not bother. If I can get . 3 off my time shifting out of 4x4 I will try next time.

 

[Dockboy]

I think in my truck you have to lift for it to disengage.



My only problem though is it launches so hard, the seat belt locks, and I can't reach the shifter anyway!! :-laf

 

[snowracer69]

shift out on the 1-2 shift. The transfer case will disengage, ie, you won't be giving power to the front end anymore, however, your axle will remain locked (if you have an axle-disconnect, pre '01. 5's I believe) and it will continue to turn. Have been practicing launching, and I shift out on the 1-2 shift... also, because I have billet throughout my transmission, as soon as I shift out of 4x4 I lock the converter... that DEFINITELY makes it pull harder, but man the 2-3 shift is a doozy! And lug the engine in 3rd... lol... even 46 psi boost and it doesn't sound quite right!

 

[John Dishong]

Thanks for the info. I also have billet throughout (inc. intermediate). I have the torque converter lock automatically as I make the 1 to 2 shift. This seems to work very well then it stays locked throughout the 2 to 3 and 3 to OD toward the end of the run. The only ting is I need to make sure the rear tires are hot or I get quite a 4 wheel drive spin going through the 60 foot mark. So for those of you that make the 1 to 2 shift out of 4 wheel, what about if the TC is locked? Anyone think of a way to get that front axle to disengage?



Thanks for the input.

 

[CumminFast]

On one launch my truck jerked out of 4wd after 3rd gear and the tires spun in 4th and 5th gear. I think at a certain power level it will have to be 4wd all the time.

 

[Rhondasway]

shift out on the 1-2 shift. The transfer case will disengage, ie, you won't be giving power to the front end anymore, however, your axle will remain locked (if you have an axle-disconnect, pre '01. 5's I believe) and it will continue to turn. Have been practicing launching, and I shift out on the 1-2 shift... also, because I have billet throughout my transmission, as soon as I shift out of 4x4 I lock the converter... that DEFINITELY makes it pull harder, but man the 2-3 shift is a doozy! And lug the engine in 3rd... lol... even 46 psi boost and it doesn't sound quite right!

This is exactly what I do, except my boost is a bit higher...

I have locked up before going out of 4x4 a couple of times and it didn't seem to make any difference, so due to my switch location, I just hit it as I come up from the 4x4 lever. I have lost traction in second at one race, but that side of the track was slick for everyone and they VHT'd it after that round.

As far as "I think at a certain power level it will have to be 4wd all the time", I must not be there yet. Maybe I should put it back to stock, including the transmission, except for my 370's to get more power... :-laf

If you're looking for mph, look closely at your tires. I used to run low psi for traction, but as I started inflating them I didn't lose noticeable traction and did gain at top end. Even if you have to leave at slightly lower boost, your mph can come up. Tires vary from type to type, so you may have to experiment or find a knowledgeable tire rep (good luck) to help meet your needs.