Auto 4WD works well in the snow and ice.

Mikewinn64 · January 5, 2023

This quote comes directly from https://www.gmc.com/gmc-life/how-to/when-to-use-four-wheel-drive

AUTOMATIC 4 HI
If road conditions frequently alternate between high- and low-traction areas, consider using the “AUTO” setting found on select GMC electronic transfer cases. This setting allows your GMC to automatically distribute torque to the front axle by anticipating the need for additional traction. Shifting into “auto” engages the front axle, but the transfer case sends power primarily to the rear wheels in normal conditions and the clutches modulate torque forward to provide stability and enhance traction to the vehicle. Although not always optimal for efficiency and wear of your vehicle 4wd driveline, AUTOMATIC 4 HI can be used on any road condition without risk of damaging your vehicle. 

Davew277 · January 5, 2023

7 hours ago, dal1980 said:

I sure hope you lumped yourself into the "people" that clearly have no idea how this system works. You're trying to make comparisons between Chrysler AWD and the four wheel drive on a 7k# HD pickup. Nonsensical forum arguments are the best, arent they! Solving the truck worlds problems one opinion at a time.

They use the same transfer case, which is why I mentioned it. It was even stated earlier in this thread. But good job at trying to pick apart a comment intended to help people. I guess you don't know that DODGE is a Chrysler. They have a 3500 too, maybe you've heard of it? They are not AWD vehicles and they have the Auto function as well. Maybe I need to post the owners manual from that vehicle too. Right back at ya!

Edited January 5, 2023 by Davew277

Jettech1 · January 5, 2023

8 minutes ago, Davew277 said:

I sure hope you lumped yourself into the "people" that clearly have no idea how this system works. You're trying to make comparisons between Chrysler AWD and the four wheel drive on a 7k# HD pickup. Nonsensical forum arguments are the best, arent they! Solving the truck worlds problems one opinion at a time.

They use the same transfer case, which is why I mentioned it. It was even stated earlier in this thread. But good job at trying to pick apart a comment intended to help people. Also, who said anything about AWD? The Jeep Auto is not AWD... Maybe I need to post the owners manual from that vehicle as well. Right back at ya!

Hey there gentlemen, how about we all meet up for a beer? Probably not possible because there's only a slight chance we all live near each other. But hey, how about an online beer?? Would that help I hope? And I'm buying!!

Edited January 5, 2023 by Jettech1

Davew277 · January 5, 2023

Nevermind.

Edited January 5, 2023 by Davew277

Jettech1 · January 5, 2023

8 minutes ago, Davew277 said:

Nevermind.

Please hang in there. Everyone has an opinion. Some are good, some are not so good. Just hang in there ok? Knowledge is to share, not to keep to yourself but to help others.

Davew277 · January 5, 2023

7 minutes ago, Jettech1 said:

Please hang in there. Everyone has an opinion. Some are good, some are not so good. Just hang in there ok? Knowledge is to share, not to keep to yourself but to help others.

Well, some people aren't open to learning. They don't even read the owner's manual because they already know it all.

I can see why this HD forum is rather small compared to most forums I've been on. It's only takes a few to ruin it for all. I don't want to deal with people like this and I don't have to. Take care!

Jettech1 · January 5, 2023

2 minutes ago, Davew277 said:

Well, some people aren't open to learning. They don't even read the owner's manual because they already know it all.

I can see why this HD forum is rather small compared to most forums I've been on. It's only takes a few to ruin it for all. I don't want to deal with people like this and I don't have to. Take care!

Be well sir. I hope nothing but the best for you!

grandpapa20_ · January 6, 2023

2 hours ago, Jettech1 said:

Be well sir. I hope nothing but the best for you!

Well damn, we all must be stupid then Dave. Have you ever worked for a Chevy dealership. I’ve seen vehicles get locked in 4wd due to being left in auto 4wd. But like I said, I guess we’re not all as smart as you.

Jettech1 · January 6, 2023

2 hours ago, grandpapa20_ said:

Well damn, we all must be stupid then Dave. Have you ever worked for a Chevy dealership. I’ve seen vehicles get locked in 4wd due to being left in auto 4wd. But like I said, I guess we’re not all as smart as you.

Ok, how about we don't judge anyone here ok?? I'm sure Dave is a smart guy and has his experiences like we've all had.. C'mon all..... we have different opinions of what we've read from GM and different real world experiences in the real world...Can we all share our real world experiences with no judgment? Please?

Pryme · January 6, 2023

We need to shine the newdude spotlight(Batman) into the sky for the final word.

@newdude

newdude · January 7, 2023

On 1/2/2023 at 6:54 PM, swathdiver said:

When in Auto, the front driveshaft is spinning. You will wear out the transfer case prematurely by leaving it in Auto, these are not AWD transfer cases with a planetary and made to run on any road surface all the time. Use it when you think you'll need it and then switch back to 2HI.

Yes, but the transfer case is engaged and spinning the front prop shaft. When the computer decides more traction is needed, it engages the front differential.

If you google around you can find a write up on how AUTO works.

On 1/3/2023 at 8:35 PM, Pryme said:

Someone earlier stated the transfer case is engaged in auto and only the front differential is disengaged until it’s needed.

I don’t have auto so I’m just sitting here with my popcorn.

On 1/4/2023 at 7:45 PM, Jettech1 said:

Would someone who please knows the answer to this question here please answer it? I have many doubts anything going forward into the transfer case is actually moving while in 4 auto mode. Why would that be the case? The 4hi mode is still there to press for full time 4wd. From what I've read, the auto mode only engages the transfer case when slippage is detected. So there should be no worries about being in auto mode, well, all the time. Is what I've read true or not? Just asking is all.

On 1/4/2023 at 9:48 PM, Davew277 said:

Auto is NOT 4wd, not by a longshot. If you want to know for sure, try going off-road using only Auto. Then switch to 4H or 4L. It's a night and day difference. I have went off-road extensively and have tried Auto in that scenario. I only use 4L on my acreage.

Auto transfers power to other wheels when the primary drive wheels (in the rear) lose traction. It is a high tech traction control system, not full fledged 4wd.

Some Chrysler models use Auto full time and have options to engage 4wd in addition to this.

Read the owners manual if you have any doubts.

There are warnings about using 4wd modes on dry pavement. There are no such warnings about using Auto on dry pavement.

I rest my case. Any further discussion from me on this subject will be redundant and therefore pointless. Do what you want.

On 1/5/2023 at 11:11 PM, Pryme said:

We need to shine the newdude spotlight(Batman) into the sky for the final word.

@newdude

Ok. Lets start at the beginning.

AUTO mode. What engages when you push that button on the dash and place it in AUTO? Believe it or not AUTO and 4HI are almost identical in their operations except for one or two key features/components.

In 4HI, you push the button, the encoder motor shifts the transfer case into 4HI and the transfer case control module also tells the front axle actuator to engage the front axle. Front axle on all of these (ZR2 models excluded) are an open diff setup. As far as inside the transfer case goes, when you apply 4HI, the encoder motor engages the 4 wheel drive clutch assembly which applies full and the 2/4 wheel actuator shaft engages to 4 wheel and power is transmitted to the front drive shaft.

In 4 AUTO, everything I said above is the exact same EXCEPT...the power output is now controlled. The front axle is locked engaged (as others have suggested its the front axle that engages and disengages in AUTO, this is incorrect). The clutch pack and the 2/4 wheel actuator shaft are what controls the power to the front if rear traction loss is predicted or occurring. The TCCM using essentially the ABS and Stabilitrak operations sees the wheel slips and acts accordingly. If there is no traction loss, the TCCM will have the actuator shaft apply little to no engagement of front axle output. The clutch will run 0-5ft.lbs of torque. As traction loss is seen, the actuator engages the shaft and the clutch engages more thus increasing outflow of power to the front. Front axle is always engaged, its power flow isn't.

TLDR, AUTO turns it into an AWD system. Transfer case is the determining factor for power flow to the front axle, not the front axle itself. This is why in AUTO you get no crow hop. There is no or little to no power to the front axle.

Can AUTO be considered a "high tech traction control system"? No. Traction control is a means of using the ECM, ABS and TCM to control wheel speed to gain traction. Fuel injectors can get cut, throttle body can be closed, ABS can be used to engage a specific wheel brake, and the TCM can upshift the transmission all methods used to CUT power to re-gain traction. Traction control is also used in braking and steering situations, something that AUTO has nothing to do with, therefore it can't be considered a traction control system.

Just in case, here's what GM has to say about it right from their service manual:

In the 4HI mode, the power flow to the rear propshaft is the same as it is in the 2WD mode. To deliver power flow to the front propshaft during the 4HI position, the transfer case control module commands the 2/4 wheel drive actuator assembly to apply the clutch to a calibrated torque. The 2/4 wheel drive actuator assembly turns the control actuator shaft. A brake in the 2/4 wheel drive actuator assembly holds the control actuator shaft in the full clutch position. The control actuator shaft is cam designed and the cam action moves the control actuator lever. The control actuator lever pivots against the control lever and moves toward the clutch pressure plate, to engage the clutch. As more pressure is applied to the clutch pressure plate, the clutch discs are compressed. Using inner clutch discs, which are engaged with the clutch hub, and the outer clutch discs, which are engaged with the clutch housing, the power flow is delivered to the clutch housing. The clutch hub is splined to the rear output shaft, and the clutch housing rotates on a needle bearing on the rear output shaft. The chain drive sprocket is splined to the clutch housing. The power flows from the drive sprocket, through the chain, to the chain driven sprocket. The driven sprocket is splined to the front output shaft. The power flow is delivered to the front propshaft through the front output shaft .

During the Auto 4WD mode, the power flow is the same as it is in the 4HI mode. Except, during the Auto 4WD mode, the 2/4 wheel drive actuator assembly rotates the control actuator shaft to the correct torque level positions. Rotating the control actuator shaft to the various positions changes the clutch torque level. When a difference of front wheel speed to rear wheel speed is recognized, the transfer case control module commands for more, or less clutch torque.

Pryme · January 8, 2023

4 hours ago, newdude said:

Ok. Lets start at the beginning.

AUTO mode. What engages when you push that button on the dash and place it in AUTO? Believe it or not AUTO and 4HI are almost identical in their operations except for one or two key features/components.

In 4HI, you push the button, the encoder motor shifts the transfer case into 4HI and the transfer case control module also tells the front axle actuator to engage the front axle. Front axle on all of these (ZR2 models excluded) are an open diff setup. As far as inside the transfer case goes, when you apply 4HI, the encoder motor engages the 4 wheel drive clutch assembly which applies full and the 2/4 wheel actuator shaft engages to 4 wheel and power is transmitted to the front drive shaft.

In 4 AUTO, everything I said above is the exact same EXCEPT...the power output is now controlled. The front axle is locked engaged (as others have suggested its the front axle that engages and disengages in AUTO, this is incorrect). The clutch pack and the 2/4 wheel actuator shaft are what controls the power to the front if rear traction loss is predicted or occurring. The TCCM using essentially the ABS and Stabilitrak operations sees the wheel slips and acts accordingly. If there is no traction loss, the TCCM will have the actuator shaft apply little to no engagement of front axle output. The clutch will run 0-5ft.lbs of torque. As traction loss is seen, the actuator engages the shaft and the clutch engages more thus increasing outflow of power to the front. Front axle is always engaged, its power flow isn't.

TLDR, AUTO turns it into an AWD system. Transfer case is the determining factor for power flow to the front axle, not the front axle itself. This is why in AUTO you get no crow hop. There is no or little to no power to the front axle.

Can AUTO be considered a "high tech traction control system"? No. Traction control is a means of using the ECM, ABS and TCM to control wheel speed to gain traction. Fuel injectors can get cut, throttle body can be closed, ABS can be used to engage a specific wheel brake, and the TCM can upshift the transmission all methods used to CUT power to re-gain traction. Traction control is also used in braking and steering situations, something that AUTO has nothing to do with, therefore it can't be considered a traction control system.

Just in case, here's what GM has to say about it right from their service manual:

In the 4HI mode, the power flow to the rear propshaft is the same as it is in the 2WD mode. To deliver power flow to the front propshaft during the 4HI position, the transfer case control module commands the 2/4 wheel drive actuator assembly to apply the clutch to a calibrated torque. The 2/4 wheel drive actuator assembly turns the control actuator shaft. A brake in the 2/4 wheel drive actuator assembly holds the control actuator shaft in the full clutch position. The control actuator shaft is cam designed and the cam action moves the control actuator lever. The control actuator lever pivots against the control lever and moves toward the clutch pressure plate, to engage the clutch. As more pressure is applied to the clutch pressure plate, the clutch discs are compressed. Using inner clutch discs, which are engaged with the clutch hub, and the outer clutch discs, which are engaged with the clutch housing, the power flow is delivered to the clutch housing. The clutch hub is splined to the rear output shaft, and the clutch housing rotates on a needle bearing on the rear output shaft. The chain drive sprocket is splined to the clutch housing. The power flows from the drive sprocket, through the chain, to the chain driven sprocket. The driven sprocket is splined to the front output shaft. The power flow is delivered to the front propshaft through the front output shaft .

During the Auto 4WD mode, the power flow is the same as it is in the 4HI mode. Except, during the Auto 4WD mode, the 2/4 wheel drive actuator assembly rotates the control actuator shaft to the correct torque level positions. Rotating the control actuator shaft to the various positions changes the clutch torque level. When a difference of front wheel speed to rear wheel speed is recognized, the transfer case control module commands for more, or less clutch torque.

Amazing write up Newdude. Thanks.

swathdiver · January 8, 2023

5 hours ago, newdude said:

In 4 AUTO, everything I said above is the exact same EXCEPT...the power output is now controlled. The front axle is locked engaged (as others have suggested its the front axle that engages and disengages in AUTO, this is incorrect).

Great explantation and I stand corrected!

Dr1ft3r · January 8, 2023

He still did not answer the question of whether or not Auto mode is safe to use on dry pavement which is where the heated discussion began.

I have watched a lot of videos and none of them specifically state that using Auto mode on dry pavement will cause a problem or premature wear.

This video was pretty thorough. But while this guy states that he will use 2wd most of the time he does not state if Auto mode will cause any issues at any time. However, he does warn about 4h and 4l and he specifically refers to them as the 4wd modes but does not include Auto in that category

https://youtu.be/mm0ZIzErAtM

Edited January 8, 2023 by Dr1ft3r
Wrong link

Jettech1 · January 8, 2023

3 hours ago, Dr1ft3r said:

He still did not answer the question of whether or not Auto mode is safe to use on dry pavement which is where the heated discussion began.

I have watched a lot of videos and none of them specifically state that using Auto mode on dry pavement will cause a problem or premature wear.

This video was pretty thorough. But while this guy states that he will use 2wd most of the time he does not state if Auto mode will cause any issues at any time. However, he does warn about 4h and 4l and he specifically refers to them as the 4wd modes but does not include Auto in that category

https://youtu.be/mm0ZIzErAtM

I've read his response actually 5 times now trying to take it all in. The one thing I didn't get from it is, is power being transferred from the transfer case to the front wheels when it 4 wheel auto? Perhaps this might be a good analogy. Ok, so I have a 2021 Explorer with the 2.3L turbo engine in it. When I want to do a burnout, one foot on the brake, one on the gas...it will burn the hell out of both tires without a limited slip rear diff. The system notices a wheel slippage from one side and will apply brakes to the other side to put power to that side as well...instantaneously.....So when in 4 auto, is the transfer case really putting power to the front differential, when not needed? Why would it? If my cheap ass Explorer can sense a different wheel spin and slippage, then apply power to the other wheel seamlessly, why wouldn't the 4 auto do the same thing? And transfer the power to the front wheels....ONLY, when needed???