trever1t

iTrader: (14)

I use 4hi on the track and on the street for wot launching. I only use 4auto for wet or slick conditions. Do like Thunder said. if you can get it back into 2wd do it as soon as you can without losing traction, for me that is after the 1-2 shift or i am wall bound

VMax

thanks man, i will give it a try.

BIRCHZ71

iTrader: (4)

i took this advice when i started putting some power down and it has worked out great for me. but i am curious if i would see any faster et's if i could get it to hook in 2wd.seems to pull harder in 2wd...maybe its just in my head.

rockerjoe2008

iTrader: (1)

Yea, I remember you guys saying switch to 2wd after the 1-2 shift. My selector is the dial style, I don't know if that makes a difference, but I doesn't seem like it is going to 2wd until after I let off the throttle. Be nice to have some definitive info one way or the other. If its not going into 2wd then I can stop focusing on turning a **** and focus more on keeping it between the ditches.

VMax

i think you are right it seems that it pulls harder in 2wd.

09Jimmy

Of course it pulls harder in 2WD. Think about it for a second. Common belief is that manual trans vehicles lose about 15% of their flywheel horsepower to driveline losses and auto vehicles lose 18%-20% due to the torque converter.4X4 trucks probably fall into the 20% category due to their heavier drivetrains. Let's say your modded engine is putting out 400 flywheel HP. That means you're probably putting out 320 rear wheel HP. Now, if you add in turning a transfer case, front driveshaft, front gears and axles and driving those heavy front wheels and tires, you must be losing another 20% of your potential Wheel HP. Now you only have 280 HP pushing 4 wheels.
Parasitic losses can amount to a fair amount of HP. Look at the difference switching to electric fans can make versus an engine driven fan. Perhaps someone who runs their truck in the 1/4 has tried it in both 2WD and 4WD, same track, same day and can post their results.

kbracing96

iTrader: (26)

In these trucks, EVERYTHING in the 4x4 drive train is always spinning in both 2wd and 4wd. The only difference is the engagement hub that locks them together is not engaged when in 2wd, so parasitic loss would be very similar in both 2wd and 4wd.

09Jimmy

I disagree. I just went out and laid under my truck and I can spin the front driveshaft with my hand, park brake on, truck in drive. When you are in autotrac, the transfer case is turning, just waiting for the computer to detect tire slippage and engage the front diff. When you are in 2WD the transfer case is not turning, that's why they came up with the autotrac system. The fuel economy would be horrendous if the transfer case, driveshaft and axles were always turning. This does not apply to a Denali with AWD.

kbracing96

iTrader: (26)

Must be new for the new trucks, because on my 01 with the NP 246 autotrac transfer case truck, I can NOT turn my front drive shaft right now with the wheels on the ground on 2wd. (also just when out and tried exactly what you said you just did)

BigCountryx

iTrader: (3)

saw a vid of an f-250 switching to 2wd too early in the run and it was all he could do to keep it out of the wall. Don't switch till well into 2nd IMO