4 wheel drive "Auto" setting

bertiman · January 6, 2016

Thanks again to everyone who posted into this thread... I guess there will never really be consensus on this feature. From what I've been able to observe with my truck:

1) Auto does allow for much greater controlled off-line acceleration than 2 wd

2) Watching the realtime mpg meter, brisk (not floored) off-line acceleration in auto runs about 2-3 mpg, while in 2 wd the meters shows about 3-4 mpg

3) There is more perceived drive-train vibrations (like a rubbing/grinding type of vibration) when accelerating in auto as compared to 2wd.

Even in dry pavement, I do like the traction the auto provides... as every once in a while, I find my back wheels don't have the grab I expected.

I guess my main outstanding question is: using only the auto setting, about how many miles of average driving would one expect to get out of the clutch pack?

SMiller · January 6, 2016

Thanks again to everyone who posted into this thread... I guess there will never really be consensus on this feature. From what I've been able to observe with my truck:

1) Auto does allow for much greater controlled off-line acceleration than 2 wd

2) Watching the realtime mpg meter, brisk (not floored) off-line acceleration in auto runs about 2-3 mpg, while in 2 wd the meters shows about 3-4 mpg

3) There is more perceived drive-train vibrations (like a rubbing/grinding type of vibration) when accelerating in auto as compared to 2wd.

Even in dry pavement, I do like the traction the auto provides... as every once in a while, I find my back wheels don't have the grab I expected.

I guess my main outstanding question is: using only the auto setting, about how many miles of average driving would one expect to get out of the clutch pack?

Slight vibration is normal as you are spinning everything up front.

I would expect a lifetime of trouble free maintenance while running auto as that is what it was designed for, having said that I really see no reason to leave it engaged in the middle of the simmer for no reason.

mdrew · January 6, 2016

Auto during the winter when snow or ice can be expected. It's saved me a few times already with black ice this winter and works quite well. Fuel consumption is up about 1.5mpg, but that's less than a deductible should I hit the ditch. Just don't get too throttle happy or you might break stuff as it slips and grabs traction.

I am curious though. Has anyone noticed a creaking type noise in the drive train when in auto, and getting out of the truck after a drive? I believe it may be some slop in the t-case, but not sure if it is normal?

I miss the AWD the older Denali's had, but auto is working well enough so far.

SMiller · January 7, 2016

Auto during the winter when snow or ice can be expected. It's saved me a few times already with black ice this winter and works quite well. Fuel consumption is up about 1.5mpg, but that's less than a deductible should I hit the ditch. Just don't get too throttle happy or you might break stuff as it slips and grabs traction.

I am curious though. Has anyone noticed a creaking type noise in the drive train when in auto, and getting out of the truck after a drive? I believe it may be some slop in the t-case, but not sure if it is normal?

I miss the AWD the older Denali's had, but auto is working well enough so far.

I will say I was always concerned when taking off from a frozen intersection when it goes from frozen solid to dry pavement that it would snap the front end or transfercase, I had a trailblazer and did a WOT rev limter take off on solid ice to dry pavement and it handled it like a boss, I would have zero concerns if you went from slick to catching traction, if it can handle WOT doing this it can stand up to some light slipping.

BootyHunter86 · January 7, 2016

2WD most of the time. Rain today so auto for me. My sister was hydroplaning like crazy on her acura, and she works pretty far so shes taking the beast to work tomorrow (Denali)

tbarn · January 7, 2016

Might as well stoke the fire

Recommendation/Instructions:
The apply plate bearing designs in these transfer cases are not rated for continuous operation. They are intended for intermittent operation only when 4WD is required.

Long periods of continuous operation have been experienced in the U.S northern border states and in the provinces of Canada. This type of operation will shorten the life of the transfer case and in particular the apply plate bearing. As a general rule transfer case selector switches should be left in the 2HI mode unless road conditions dictate otherwise.

The following is a guideline for the proper use of 4WD in Magna transfer cases RPO's NP1, NP8, NQH and NQF.

1. 2HI mode sends all of the drive train torque to the rear wheels. This provides the most fuel efficient driving mode.
2. Auto/4WD mode when engaged constantly monitors the vehicle's drivetrain to provide optimum traction as road conditions dictate. Torque is automatically transferred to the front wheels to provide seamless 4WD operation. Auto mode is intended for on-road driving that includes rain, snow, ice and gravel.
3. 4HI provides enhanced traction for snow, ice, and gravel and most off road conditions. It is not intended for use on dry pavement.
4. 4LO provides enhanced traction and increased torque multiplication to handle extreme on and off road conditions such as steep hills, deep sand, mud, snow and ice. 4LO can also be used during boat launch operations for increased torque availability.

Note: 2–4 Not intended for continuous operation.

NQH is the common transfer case used on these 14-16 K trucks. Among others.

bertiman · January 7, 2016

Might as well stoke the fire

Recommendation/Instructions:

The apply plate bearing designs in these transfer cases are not rated for continuous operation. They are intended for intermittent operation only when 4WD is required.

Long periods of continuous operation have been experienced in the U.S northern border states and in the provinces of Canada. This type of operation will shorten the life of the transfer case and in particular the apply plate bearing. As a general rule transfer case selector switches should be left in the 2HI mode unless road conditions dictate otherwise.

The following is a guideline for the proper use of 4WD in Magna transfer cases RPO's NP1, NP8, NQH and NQF.

1. 2HI mode sends all of the drive train torque to the rear wheels. This provides the most fuel efficient driving mode.

2. Auto/4WD mode when engaged constantly monitors the vehicle's drivetrain to provide optimum traction as road conditions dictate. Torque is automatically transferred to the front wheels to provide seamless 4WD operation. Auto mode is intended for on-road driving that includes rain, snow, ice and gravel.

3. 4HI provides enhanced traction for snow, ice, and gravel and most off road conditions. It is not intended for use on dry pavement.

4. 4LO provides enhanced traction and increased torque multiplication to handle extreme on and off road conditions such as steep hills, deep sand, mud, snow and ice. 4LO can also be used during boat launch operations for increased torque availability.

Note: 2–4 Not intended for continuous operation.

NQH is the common transfer case used on these 14-16 K trucks. Among others.

Figures.... I've been driving in auto mode for the past few days and I MUCH prefer it over the 2wd mode. It seems that the transmission is much more natural, fluid and responsive in auto mode. I don't find any of the transmission lag when in auto mode. In 2wd, the transmission seems to want to stay in the lower rpm range and needs more coaxing to get to the gear needed. In the auto mode, it is more aggressive in its gear choice and feels much more responsive. Also, I noticed that AFM seems to work more intelligently/smoothly in auto mode than 2wd mode. At least in terms of when it switched from 8 to 4 and back. I don't really have any good mpg indicators as traffic has been brutal the last few days.

J-NO · January 8, 2016

New member here. First post.

Living in Vancouver, BC, where it always rains, I always used Auto in my 2009 Sierra. No issues for the 6 years I owned it and 140,000 kms. I would take it out mid-summer when it was dry but for 40-45 weeks a year it was in Auto. I felt more confident in the truck in the rain, loose gravel/sand, ice/snow, etc.

Just picked up my 2015 LTZ in November and switched it to Auto immediately. After browsing this topic a few days ago I decided to see if the fuel economy theory was significant. I wasn't in 2WD for even an hour when my ass end slid out while making a left turn in the rain. Needless to say right back into Auto and in Auto is where it will stay.

mike5511 · January 8, 2016

I know two people that got jerked into the ditch on icy roads while in the Auto mode. I said icy as in freezing rain kind of roads.....not really any way to drive on those safely unless you have studded tires and neither of them did. If you've driven on ice much, you know forward momentum is sometimes the only thing that keeps you moving forward. If you stop, the vehicle will slide sideways or backwards depending on the slope of the road. Any little input can cause a change in direction. This is what both drivers, experienced drivers mind you, determined caused their accident. The auto 4wd kicked in and jerked the vehicle to the left and off the road.....both of these were on paved county roads that used to be dirt roads not many years ago, no shoulders and narrow. FWIW

TJay74 · January 8, 2016

I will always say this, I have driven vehicles with HP from 200 to 500hp. Most all of them RWD vehicles, never needed "auto" or 4wd/AWD in order to be able to drive on rain soaked roads. Common sense tells you to take it easy and of course a RWD vehicle can get loose on the rear end if you are on it hard enough going around corners. I liven in Wichita KS for a year driving a 2001 Formula Firebird that had almost 400hp to the rear wheels on summer tires. Never had an issue getting around, took my time and drove safe and made it each time.

I never use auto in this truck or any of the 2 prior 4wd GM trucks that had auto before it. Mine doesn't move to 4wd unless there is snow/ice on the ground or if I am going off road where I know I will need the extra traction.

SMiller · January 8, 2016

I will always say this, I have driven vehicles with HP from 200 to 500hp. Most all of them RWD vehicles, never needed "auto" or 4wd/AWD in order to be able to drive on rain soaked roads. Common sense tells you to take it easy and of course a RWD vehicle can get loose on the rear end if you are on it hard enough going around corners. I liven in Wichita KS for a year driving a 2001 Formula Firebird that had almost 400hp to the rear wheels on summer tires. Never had an issue getting around, took my time and drove safe and made it each time.

I never use auto in this truck or any of the 2 prior 4wd GM trucks that had auto before it. Mine doesn't move to 4wd unless there is snow/ice on the ground or if I am going off road where I know I will need the extra traction.

Cool story bro

Why even have 4wd, sounds like you are a good enough driver that its not even needed.

Auto mode is there to use, why not use it?

robvas · January 8, 2016

I don't use auto in the rain - no point

TJay74 · January 8, 2016

Cool story bro

Why even have 4wd, sounds like you are a good enough driver that its not even needed.

Auto mode is there to use, why not use it?

Why, because I am part of outage restoration for an electric utility company. No matter the weather I am required to come into work in order to help get the lights back on for people. Plus the fact that 4wd is only $2k more than 2wd and has better resale down the road is a win/win for me. My dad always told me the only truck worth owning is a 4wd truck, better to have and not need 4wd then to be stuck when you don't have it.

Rawyzf · January 8, 2016

Cool story bro

Why even have 4wd, sounds like you are a good enough driver that its not even needed.

Auto mode is there to use, why not use it?

Don't be a dick, he's just stating his usage and experience.

To each their own.

Auto mode is there, and each will use it as they please. That comfort level is different for everyone.

mdrew · January 9, 2016

I will say I was always concerned when taking off from a frozen intersection when it goes from frozen solid to dry pavement that it would snap the front end or transfercase, I had a trailblazer and did a WOT rev limter take off on solid ice to dry pavement and it handled it like a boss, I would have zero concerns if you went from slick to catching traction, if it can handle WOT doing this it can stand up to some light slipping.

Are you actaully being serious? Ever rebuilt a transmission, differential, or t-case?

It is that kind of ignorant and irresponsible behavior that GM is as conservative with power reduction programming as they are. And people complain about it, well this is why.