2 or Auto

Donstar · January 12, 2017

You can drive as fast as you want in auto.

It should be labeled "AWD" instead of "auto 4wd"

AWD and Auto 4WD are terms that distinguish between different operating systems. They mean quite different things to me and should not be interchangeable, imo. Many people don't care and your suggestion would go unchallenged by them.. There are some good explanations and references regarding the distinction between the two in this thread.

Silverado Steve · January 12, 2017

Contrary to this particular discussion, I have never said bad things will happen if you leave our trucks in 4 auto, in fact I believe in the other topic that Truckguy got into it a few months back on whether it was safe to use 4 auto for extended periods of time, I sided with him. However, I think we both agree that over time prolonged use of 4 auto will accelerate wear on the front drive components. What that time is, who knows. These trucks could easily go well past 100,000 miles in 4 auto and they could crap out before then, who really knows. My only take on that is, if GM designed the 4 Auto function to resemble AWD as truckguy states, why would they add a 2wd mode? It even states in the OM that the use of 4 auto should be used in slippery traction conditions, no where does it state that you should use it as the primary setting for driving. If you do, feel free, I'm not projecting impending failure; however 4 auto is not the same mechanically as AWD and is not designed to be so, or else there wouldn't be the blurb in the OM.

On another note, you are incorrect in your assumption that my truck is the only GM 4wd vehicle I have ever owned. I don't know where you came up with that. I owned an S-10 Blazer black in high school with the crappy 2.8 v-6 and more recently a 2005 Trailblazer which I believe also had 4 auto as well.

My dad leaves it in 4auto all winter. A buddy leaves it in 4auto always. I leave it in 4auto when there is a chance I'll be encountering snow or ice covered roads, and more than once I've left it on 4auto for weeks after pulling my boat up a slippery boat ramp.

I saw an article a few years ago where a GM engineer said they assumed people just leave it on.

Steve seems to be implying you shouldn't ever do these things and in a way, he's right. If you never put your truck in 4wd you will never any wear and tear on the 4 wheel drive components.

However; Steve's 2014 is his first 4wd GM truck. My dad, our friends, and I have all been using the auto 4 on a lot of trucks over a lot of years without any issues. (I can't remember when I got my first auto Silverado, but I know I've had at least 6-7)

Every now and again you see a rare case of someone that had trouble with it, but you've got a drivetrain warranty. Beyond that, I've never heard of anyone I know having trouble with it, and we pretty much all drive 4wd trucks in Wisconsin. (my dad, my brother, my step brothers all drive GM trucks, as well as many of our friends) A LOT of Midwest men tow boats, atvs, snowmobiles, wave runners, hauls canoes/kayaks/dirt bikes, and go off road fishing and hunting. It's the lifestyle here, and we use the auto 4, it's a lot easier than trying to remember switching in and out of 4 hi. (not to mention our roads are snow covered a lot)

YMMV, but we've been using auto 4 for a lot of years in the Midwest, on the highway and off.

Silverado Steve · January 12, 2017

Again, your questions are answered very clearly in the link I posted. I recommend you read it before you challenge what I stated which is stated in these links. The advantage of 4wd over AWD in off-roading is the fact the transfer case has a low gearing (4LO) which is much more beneficial in rock crawling or deep mud, where an AWD system will not be able to control the spinning of all 4wheels to go at the same low speed like 4LO.

http://www.digitaltrends.com/cars/whats-the-difference-between-four-wheel-drive-and-all-wheel-drive/

From the reading:

" The biggest difference between 4WD and AWD is that an AWD drive system is on all the time. Well, mostly. But we’ll get to that, as there are two types of all-wheel drive: mechanical and electronic.

The most common way of accomplishing a capable, mechanical AWD system is by using three differentials. A differential is a box of gears, a.k.a. engineering magic, that can take power from the transmission and split it at different levels between two wheels or the front and rear axles (four wheels).

Related: Learn the differences between FWD, RWD, AWD, and 4WD

In AWD, this system works to get power to the wheels with the most traction by splitting power between the front and rear axels on the center differential, and the individual wheels by way of the front and rear differentials.

AWD isn’t quite as robust as 4WD and it can’t match the same levels of traction in extremely low-speed off-roading that the older 4WD systems provide. But AWD does have some clear advantages."

The only way cheaper awd systems control each wheel is by applying brakes the wheel that spins. If you want to say there is some big difference between auto4 and awd because of that, ok. But it is incorrect to say awd "controls each wheel independently"

If awd had full control of each tire, then it would be god like in off road situations, but they aren't.

SouthernSilveradoGuy85 · January 12, 2017

An AWD system is able to send a certain amount of power to a certain wheel while this 4WD system can't. A 4WD system sends 50/50 and is either on or off. An AWD system is more complex and also doesn't have the low gear option like a 4WD system has. 4 auto is for inconsistent conditions such has where it snowed and while melting there are spots of now and/or ice and slush with spots that are just dry or wet. Also AWD you can't turn on or off, it's full time where as a 4WD system you can go between 2 and 4 and even auto 4 isn't always in 4WD. Plus unless you have some kind of locking diff (example, like the G80 rear end) then only 1 tire on the front has power going to it while in 4WD where as an AWD system has power going to all 4.

But hey, I'm sure the same people that think 4 auto is the same as AWD is the same people that think 4 auto is needed in simple rain. However did I make it home in my '86 2wd C10 and my '98 Z71 that didn't have the 4 auto option. Better yet, how ever did people make it home in a high performance RWD car in the rain I'll never know. I guess there's a lot of lucky people.

newdude · January 12, 2017

We've been over this a few times. Last time we hashed out that Subaru currently uses 3 different systems, so comparing the pickups to them gets confusing, especially since it's an entirely different system.

2hi: transfer case and front axle disengaged.

4auto: front axle engaged, transfer case engaged at a very small torque, and ramped up as needed, up to a full lock.

4hi: front axle engaged, transfer case locked to send same power to both ends, all the time.

I literally read all 4 pages. You are the only one who pretty much hit the nail on the head, with out going overboard on description and arguing LOL. Its a giant pissing match about who thinks they know more about AWD and AUTO 4x4 and 4x4.

Before anyone else posts, read this quote I quoted from kstruckcountry.

Those worried over the torque split, in AUTO, its 5% front and 95% rear when no slip is detected. As slip in the rear is detected (via wheel speed, etc.) the clutch pack in the transfer case starts to engage and pump more power (increase the torque to the front axle).

truckguy82 · January 12, 2017

A 4WD system sends 50/50 and is either on or off.

This is exactly what everybody thinks happens with auto4, and what I used to think.

Auto4 has an infinitely variable torque split unlike a 4wd on/off switch, this is exactly why it's like an awd system

truckguy82 · January 12, 2017

From the reading:

" The biggest difference between 4WD and AWD is that an AWD drive system is on all the time. Well, mostly. But we’ll get to that, as there are two types of all-wheel drive: mechanical and electronic.

The most common way of accomplishing a capable, mechanical AWD system is by using three differentials.

EXACTLY! This is exactly why I consider why 4auto very similar to awd.

4auto uses 3 differentials, front, rear, and center

4hi only has 2 because it locks the center

When we switch to 4auto, we are engaging the center differential

When we switch to 4hi, we lock the center differential, making it no longer a "differential"

Silverado Steve · January 12, 2017

Don't confuse the transfer case of our system with a center slip differential of that of an AWD system. This is the inherent difference between both systems, perhaps this is where your understanding is causing confusion. The center differential acts ver much like the limited slip/locker like our rear diff. There is no gearing to change into a low range like a transfer case. Also with a transfer case, there is no device to adjust power to the front axle or wheels, it's either 50% power or none.

EXACTLY! This is exactly why I consider why 4auto very similar to awd.

4auto uses 3 differentials, front, rear, and center

4hi only has 2 because it locks the center

When we switch to 4auto, we are engaging the center differential

When we switch to 4hi, we lock the center differential, making it no longer a "differential"

Silverado Steve · January 12, 2017

You've said this several times over, do you have some info you can throw up that supports this? Every piece of info I have ever read about our system states it's either on or off, never that our transfer case or front diff manages any torque or power to the front axle or wheel, it's wither locked to receive 50% power or not. There is no locker or slip differential on our front axle, thus if you get tire spin on the front left wheel, there is no device that will reroute power to the front right.

This is exactly what everybody thinks happens with auto4, and what I used to think.

Auto4 has an infinitely variable torque split unlike a 4wd on/off switch, this is exactly why it's like an awd system

Brian S. · January 12, 2017

Steve mostly I was commenting on your response that it was incorrect to say you can't drive auto as fast as you want on the first page.

I've driven it on the freeway in the summer, it's not like the 4Hi speed restricted options.

In any case, I think this debate will go on as long as there are trucks because a few people do manage to damage pieces of their drivetrain allegedly.

I just wanted the OP to know in my region of the world a lot of people use it a lot. It's the main reason I buy GMC trucks.

truckguy82 · January 12, 2017

You've said this several times over, do you have some info you can throw up that supports this? Every piece of info I have ever read about our system states it's either on or off, never that our transfer case or front diff manages any torque or power to the front axle or wheel, it's wither locked to receive 50% power or not. There is no locker or slip differential on our front axle, thus if you get tire spin on the front left wheel, there is no device that will reroute power to the front right.

This is exactly why our views our different. I'd completely agree with you if 4auto locked the front with the rear like an on-off switch. I have to find proof, it's literally just from reading extremely knowledgeable posts online of how the system works.

Also you're right, there is no limited slip or locker on the front diff, but I have an awd acura rdx in my driveway right now that doesn't either on front or back. It's a cheap type of AWD system that is probably the most common out there. If the front right tire is spinning, all it does is apply the brakes to that tire which forces the front left tire to spin. Overall it doesn't really work all that well. My truck in auto4 without a doubt provides more traction than the awd system in the acura, wet, dry, snow, or off road. I can tell because they have almost the exact same 0-60 in the dry. As soon as it rains out, the rdx will just spin if you try to launch it, and the truck will launch much harder. The acura even has much better tires for wet traction.

Silverado Steve · January 12, 2017

Brain,

My reply on the first page of "incorrect" was not in response that you can or can't drive as fast as you want, it was in reply to the response that 4 auto should be labeled "AWD" In retrospect, I think it was more important to focus on the question the OP had which was is it safe to go at a higher speed which I believe is yes, not focus on truckguys response that AWD=4 Auto which is where we are now.

The ongoing debate is negligible; however since we are on an auto enthusiast site, the semantics of minute differences do have bigger meanings in these type of forums. Go on a Subaru forum as say your car has 4wd and you will be quickly corrected. Go on a Off-Roading site like TTORA and say your Toyota Tacoma has All Wheel Drive and all hell will break loose. This conversation is like saying Android and IPhone IOS are the same....they do the same thing, but the internal parts are vastly difference which only matters to the enthusiast crowd, not the casual crowd.

Steve mostly I was commenting on your response that it was incorrect to say you can drive auto as fast as you want on the first page.

I've driven it on the freeway in the summer, it's not like the 4Hi speed restricted options.

In any case, I think this debate will go on as long as there are trucks because a few people do manage to damage pieces of their drivetrain allegedly.

I just wanted the OP to know in my region of the world a lot of people use it a lot. It's the main reason I buy GMC trucks.

phabejhmoob · January 12, 2017

Funny read, good arguments but I have both a Subaru (2 vehicles) and this truck. Sadly, I must say it is not the same as Subaru's AWD. Symmetrical, 4 wheels spinning evenly at the same time. in "auto" on the truck, it only engages when it loses traction does it not? So stop comparing all-the-time AWD with auto already.

Any case, to OPs original question, yes drive it as fast as you want.

Sean403 · January 13, 2017

Plus unless you have some kind of locking diff (example, like the G80 rear end) then only 1 tire on the front has power going to it while in 4WD where as an AWD system has power going to all 4.

This isn't true. It all depends on the configuration and types of differentials. My wife's Nissan Rouge is 'awd' with open front and rear diffs. Basically it is 1 wheel drive.

At least with the g80 I am getting 3wd. In my opinion for true 4wd you need locking diffs front and rear.