Launching in 4H

[2boosted]

I launch in 4HI then switch to 2HI...Not sure if it's really doing anything but supposedly the front hubs are unlocked in 2HI. In AUTO, my hubs are locked but the front diff is not active. I'm not sure how fast you can go in 2HI...I guess until parts give out but I'm not sure when that would occur. I wouldn't think there is anything that wouldn't handle 110 or so up front, even engaged. I could be completely wrong though.

My experience has shown that launching in 4HI vs 2HI only makes a difference on slick pavement (rain, etc). I haven't noticed appreciable differences on dry pavement.

Read ur sign, and we have almost same mods.....

I launch in 4HI, and never take it off, cause I feel there's no time.

My last pass was 12.74 and so far I only can launch in 4hi, it is usless for me in 2HI, can spin the whole strip and never get traction. I'm on 24's with nitto 315-35-24

So for me at the strip the 4hi is a most.

In the street is also a need, cause, If a ricer just happen to tease me...and roll race, once the turbo hits, my truck goes butt to the left endagering everyone...so at street, if I wanna race, need 4hi too.

So long I have hit 115+ mph have not granead the front internals...YET !

[Sizzle Chest]

I launch in 4 hi with a manual shift transfer case so don't have the option to shift out. Holding up with 115mph traps. For those that question if it helps or not, I dead hook spaying a 175 shot out of the hole on General Grabber street tires (1.65 60ft). Try that in 2 wheel drive.

The best place to get information on it is on the diesel/duramax forums and there are tricks/parts to keep the front end down an avoid unloading the front tires through weight transfer depending on your power level.

Any more power on my truck and I'll probably switch over to 2 wheel drive though. Will take some big slicks and and major suspension work to keep my 60where it is now but a safer way to go in my opinion if you're looking to go really fast.

[2boosted]

I launch in 4 hi with a manual shift transfer case so don't have the option to shift out. Holding up with 115mph traps.

I also have the manual transfer case...

4hi is great for launching.....probably AWD is better when cornering an stuff, but I dont see many of you guys protouring ur trucks.

I have used the 4hi in heavy climate condition in narrow curvy roads for 3+ hours trips over 85 and still counting.....

So I'm gonna tell ya if 4HI might hold at mid 11's soon.....

[rutroe]

Read ur sign, and we have almost same mods.....

I launch in 4HI, and never take it off, cause I feel there's no time.

My last pass was 12.74 and so far I only can launch in 4hi, it is usless for me in 2HI, can spin the whole strip and never get traction. I'm on 24's with nitto 315-35-24

So for me at the strip the 4hi is a most.

In the street is also a need, cause, If a ricer just happen to tease me...and roll race, once the turbo hits, my truck goes butt to the left endagering everyone...so at street, if I wanna race, need 4hi too.

So long I have hit 115+ mph have not granead the front internals...YET !

Yeah...I havent' run enough to really compare 2 vs 4. I have the electronic shift between 2 and 4 so switching is easy. If we have the same mods, congrats on the sub-13's. I have not run my truck since swapping the 5.3 for the 6.0...waiting on a 80E swap. But I'm thinking I should be very low 13s or high 12s. Do you have a CCSB as well?

[2boosted]

Yeah...I havent' run enough to really compare 2 vs 4. I have the electronic shift between 2 and 4 so switching is easy. If we have the same mods, congrats on the sub-13's. I have not run my truck since swapping the 5.3 for the 6.0...waiting on a 80E swap. But I'm thinking I should be very low 13s or high 12s. Do you have a CCSB as well?

Nope, RCSB 2002

That's a lot of weight off, but I'm sure you'll be mid 12 easy.

I have to learn how to launch on some boost, that I haven't

I'm not sure but the logic dictates that even if you could press that 2h button, chances are it won't disengage until you realease the go pedal !!!

Correct me if I'm wrong !

[bangbangskeetskeet]

I've never done a 4WD launch at the track but have on the street a few times. I will say there is definitely more traction but also definitely a loss of power. Where you would light the tires up in a blaze of smoke there is no spinning just going.

Just for some references...I have ran a buddy with a Titan from a dig in both 2hi and 4hi. I had a lot more sucess in 2hi. In 4hi I did have more traction but it took forever to get this thing going...my 1-2 shift is at 6100...it felt like it took a day and a half to get up and through the shift. In 2hi I spun a little but it pulled a lot harder and was through the shift in no time.

Now for how fast you can go...I use 4hi the 2 or 3 days a year it rains here in Arizona. Not because I am afraid of driving in the rain...I've driven in worse...but because i don't trust the retards who drive here and I would rather be able to throttle out of a situation than slam on the brakes, lock them up, and cause a 46898642145890998765431 car pile up. Anyways last time it rained I was out drivin around and the same buddy with the Titan wanted to roll race...65 or 70 roll if I remember correctly...he doesn't have 4wd so when we went he spun and I just took off. Went all the way up to....according to the RPM calculator....135 and it was just fine. I've even used it since then in the mud/sand with no problems.

So IMO a bolt on truck doesn't need to launch in 4hi because of the paracitic loss of power it causes. Now a big power turbo, blown, or nitrous truck could use it cuz they have more power to make up the difference with. Just my

[foggy]

Nope, RCSB 2002

I'm not sure but the logic dictates that even if you could press that 2h button, chances are it won't disengage until you realease the go pedal !!!

Correct me if I'm wrong !

I Launch in 4wd and Hit the 2h button before it shifts into second. Mine does disengage 4wd at the shift.

[rutroe]

Nope, RCSB 2002

That's a lot of weight off, but I'm sure you'll be mid 12 easy.

I have to learn how to launch on some boost, that I haven't

I'm not sure but the logic dictates that even if you could press that 2h button, chances are it won't disengage until you realease the go pedal !!!

Correct me if I'm wrong !

I dunno on that one...Foggy's answer above seems reasonable. The lights on my electronic shift knob switch to 2HI but I'm not sure that's proof that anything changed...

[Smoker_98]

Thanks for the info guys, good stuff!

[Sambo]

Read ur sign, and we have almost same mods.....

I launch in 4HI, and never take it off, cause I feel there's no time.

My last pass was 12.74 and so far I only can launch in 4hi, it is usless for me in 2HI, can spin the whole strip and never get traction. I'm on 24's with nitto 315-35-24

So for me at the strip the 4hi is a most.

In the street is also a need, cause, If a ricer just happen to tease me...and roll race, once the turbo hits, my truck goes butt to the left endagering everyone...so at street, if I wanna race, need 4hi too.

So long I have hit 115+ mph have not granead the front internals...YET !

I have pretty much done the same as this fella. I always launch in 4hi then switch to 2hi after the 1-2 shift. I accidently left it in 4wd on one run at the track and my trap speed was considerably lower. I have the electronic shift 4wd, seems to make a difference on the top end if you shift out. Seems that I cant launch with over 5 or 6psi of boost off the line or my truck will spin in 4wd, I got sideways in 4wd on one run at sar. I have similar mods as rutroe.