Launching in 4H

[Smoker_98]

I tried to search, did not find much. How many of you guys launch in 4H? How fast can you go in 4H? I did find one post about launching in 4H and shifting to 2H once you get going. I was not aware you could "shift on the fly" like that?? I feel like such a . Thanks guys.

[pl4yboy]

Shifting out of 4hi while going doesn't do anything if I remember correctly.

[tanz45]

People talk about doing it.

On these trucks the front drive shaft is always spinning (Auto 4wd NP246), so all you are doing is disengaging the front diff for the most part. I would think anyway.

[Smoker_98]

People talk about doing it.

On these trucks the front drive shaft is always spinning (Auto 4wd NP246), so all you are doing is disengaging the front diff for the most part. I would think anyway.

Thanks guys, so how fast can you go in 4H? What about in snow while your turning and such? 60?

[tanz45]

Thanks guys, so how fast can you go in 4H? What about in snow while your turning and such? 60?

They proper max speed i think is 55, after that the drivetrain differences may come into play and wheel speeds might try to be different. I don't know. I have forgotten i was in 4wd and have done 85 in the TB, so........

[DigitalBoy0101]

Thanks guys, so how fast can you go in 4H? What about in snow while your turning and such? 60?

On snow, you can go as fast as conditions allow in 4HI with no worries. I've done 80-85 for a good 15 miles (noone on the road but me), just haven't taken a longer trip than that yet. I usually use Auto though, and 4HI for only the worst driving conditions. I consider Auto the "dummy mode" that won't allow me to tear stuff up.....and so I use it as much as possible

Even using Auto, I can easily cruise at 60 when other vehicles are only crawling along at 35ish. If visibility won't allow me to see the slowpokes I reduce speed accordingly. And I don't always go that fast in a blizzard.....just because you "can" go that fast doesn't mean you have to.

Just remember that on snow your acceleration traction is MUCH better than your braking traction and you'll be fine. Watch out for bridge icing.

Now, going in a straight line without snow/ice/rain to allow some slippage (which is mostly what you're concerned with I assume, and not my snow driving lessons), I'm not sure I'd push it past 60....and even then only for a short stretch. For more than that, you want either AWD or FULL-Time 4WD like on some '70s and '80s trucks. Yes, they are different.

[CHEVROLADE]

good thread,ive always wondered this as well,i want a rcsb 4x4,,lower it down and make it fast!!but i also wanted to know if u race on 4hi and keep it there or push the button back to 2hi?also what r the weak points of racing in 4wd?reason is i like to street race and 2wd dont cut it.

[rutroe]

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.

[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.