2018 Sierra 1500 launching in auto 4wd

[Sharp780]

Hey all kinda still new to these trucks. Was playing around the other day and just did afew light launches while the truck was in auto 4wd. Only honestly tried it cause I seen the armageddon turbo video where the guy said gm did such a good job with the system that it launches like a gtr.

 

Is there a relatively high chance of something getting damaged launching it in auto 4wd? Or is that totally fine.

 

 

 

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[2018GMC]

Here is how I understand it. auto 4wd engages front driveshaft. Truck is in 2wd until slip detected. Once slip detected, clutches in the transfer case engage to activate power to front drive axle. 

 

I assume you will wear the clutches a bit in the transfer case. 

 

Remember front axle cv shafts always are engaged, even in 2wd.

 

Auto and 4x4 engauges front driveshaft. 

Edited March 15, 2019 by 2009GMC

[2018GMC]

4hi / 4lo locks front driveshaft and axle to provide power at all times. 

 

Not it recommended on dry pavement due to increased wear on drivetrain and tires. 

[Jacoby]

If you’re gonna be drag racing I’d launch in 4hi. 

[damnthetorpedoes]

There are a lot of people who would tell you to launch in 4hi and switch to 2hi after the 1-2 shift. I haven't done any launches with my truck, but that seems like it would be a pretty safe way of doing it. I can imagine that the Auto 4 would put a pretty high amount of stress on the t-case. 

[Sharp780]

Ya after doing some research I see most people suggest if your gonna launch do it in 4 hi.

Only did 2-3 mild launches in auto so I dont think it wore on things to bad hopefully

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[Gorske]

I've always launched min in 4hi and switched to 2wd just before the 1-2 shift. I try not to do that many hard launched anymore running a ProCharger and I don't want to push it. Here is my launch video I made and my most current run. The top end run I waited till 2nd to which out due to traction issues in 4wd.

 

[truckguy82]

I’ve launched my bb tuned 6.2 in 4auto and switched it to 2wd at the top of 1st atleast 200 times. Not a single issue or even symtpom of an issue.

[truckguy82]

On 3/15/2019 at 7:50 PM, 2009GMC said:

4hi / 4lo locks front driveshaft and axle to provide power at all times. 

 

Not it recommended on dry pavement due to increased wear on drivetrain and tires. 

The only reason they don’t recommend it on dry pavement is because it would be too confusing to say, “you can use this on dry pavement, just as long as you don’t turn”

[TRKLGND]

Launch in 4hi, keep it in a straight line and have fun.  No need to switch back to 2wd unless you are running it up to the speed limiter (99mph).

[ic3man5]

I always launch in auto, I've done it a million times and its still going strong. 4WD lock will put a lot of stress on the t-case because its always locked, auto decouples it most of the time. You lose about 20ms of traction in auto mode vs 4WD, I'll take that over added stress on the driveline.

 

If you aren't turning traction control off to raise stall point its even less needed. The truck has so much torque management all over the place the ECU won't let you destroy anything.

 

 

edit: I also usually never use 4WD unless I'm in really muddy conditions. Stabilitrac and braking works a million times better when its in AWD and not 4WD because it can brake each wheel better.

Edited March 24, 2019 by ic3man5

[M1ck3y]

You must have a 5.3?

[Mike GMC]

On 3/23/2019 at 7:06 PM, ic3man5 said:

I always launch in auto, I've done it a million times and its still going strong. 4WD lock will put a lot of stress on the t-case because its always locked, auto decouples it most of the time. You lose about 20ms of traction in auto mode vs 4WD, I'll take that over added stress on the driveline.

 

If you aren't turning traction control off to raise stall point its even less needed. The truck has so much torque management all over the place the ECU won't let you destroy anything.

 

 

edit: I also usually never use 4WD unless I'm in really muddy conditions. Stabilitrac and braking works a million times better when its in AWD and not 4WD because it can brake each wheel better.

Turning off TC raises the stall point on the converter?  How much?

[ic3man5]

7 minutes ago, Mike GMC said:

Turning off TC raises the stall point on the converter?  How much?

It turns off all limiters so it will go to the actual stall point (2500 RPMs)

[Mike GMC]

Cool.  This is something I will need to try!