Auto vs 2H Settings...

[truckguy82]

Then what was the full time 4wd system of the 70s...that had a lockable transfercase with a internal differential...

 

[emoji3]

 

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It was mostly likely a standard awd system with a center locking diff, also pretty nice. But the downside to that is you can't run it in 2wd. That's really the best part about our trucks system.

 

It can be 2wd, sorta awd, and 4wd

 

They each have their benefits and we are very close to having the best of all worlds.

[Knotsure]

Of course a wet road has less traction than a dry road. But, I'm just saying the same thing I said in the other thread, that auto4 in the rain is overkill in my opinion and it's not using it as it was designed. Think about this. Stop at the very bottom of a steep hill while it's raining. then try to go up it. You won't have any trouble getting up the hill even though it's less traction than on dry pavement. Then do the same thing on a snow covered road. You either will have to have it in 4 or it will be very hard in 2wd. I just don't think a wet road is enough of a traction loss to use auto4.

Again. You are using your own opinion to decide what you think GM designed it for. You say it is not designed for use in rain. I say it is designed for use in the rain. We are using our opinion to decide what we do. GM didn't say in snowy or icey inconsistent conditions, they said inconsistent conditions. And they also say you will NOT cause harm by using it on ANY ROAD CONDITION. It may cause added wear to the 4x4 driveline. I think the GM 4x4 is made to last regardless so this doesn't bother me at all.

 

I don't have to adjust my already defensive driving style to the wet roadway, I use auto4 along with my experience and knowledge as as someone who drives a truck for a living.

 

 

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[SouthernSilveradoGuy85]

Again. You are using your own opinion to decide what you think GM designed it for. You say it is not designed for use in rain. I say it is designed for use in the rain. We are using our opinion to decide what we do. GM didn't say in snowy or icey inconsistent conditions, they said inconsistent conditions. And they also say you will NOT cause harm by using it on ANY ROAD CONDITION. It may cause added wear to the 4x4 driveline. I think the GM 4x4 is made to last regardless so this doesn't bother me at all.

 

I don't have to adjust my already defensive driving style to the wet roadway, I use auto4 along with my experience and knowledge as as someone who drives a truck for a living.

 

 

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Well I tried out trucking myself and have experience with straight trucks. That actually helps me not to feel like I need auto4 on for rain. You adjust your driving for the conditions in a commercial truck just like you would in a passenger vehicle. But, we're just going in circles so no reason to keep saying the same thing time after time.

[truckguy82]

 

Me too.

 

Those of you who think you need 4 auto in the rain to pull out of a driveway are forgetting one lesson from driver's ed: YOU need to adjust your driving for the conditions. If you can't pull out without spinning your tires, YOU are giving it too much throttle, or your tires are bald. Both are problems that you should correct. if you need to peel out to pull out into traffic, it sounds like you don't have a large enough gap to safely proceed. I know some areas have a lot of traffic, so maybe you need to wait longer until the light turns red up the road. Yea traffic sucks, but you can't drive like you're in a race-car if the road is wet and there is heavy traffic anyway.

In nj we have intersections you have no choice.

 

You can wait there for, no exxageration, 10 minutes if you don't "thread the needle" and find an opening.

 

It's mandatory in some places.

 

All 4 of my tires provide braking, all 4 provide the ability to turn, it is no doubt safest to have all 4 accelerate.

 

I've never had an issue with 2wd in the wet until this truck, I have no idea how anybody manages in 2wd unless you live in a relaxed driving rural area. It's such a pain in the ass. I simply cannot turn and accelerate with more than 5-10% throttle. That's like most cars in the snow.

 

The goodyear sra's, an unloaded bed, an incosistant throttle, and a ton of power all conspire to make it the worst performing 2wd in the wet ever created. I've never driven anything even close as bad as this except a motorcycle with cold tires.

[sdeeter19555]

It was mostly likely a standard awd system with a center locking diff, also pretty nice. But the downside to that is you can't run it in 2wd. That's really the best part about our trucks system.

 

It can be 2wd, sorta awd, and 4wd

 

They each have their benefits and we are very close to having the best of all worlds.

For those that remember, those systems with the NP203 were some of the best for mixed driving out there...snow, sleet, wet, dry, all in the same mile, didn't matter.

 

I would take one of those systems over any "modern" 4wd system out there if for nothing else but brute strength and simplicity. All the strengths of a true 4wd, the driveability of an AWD.

 

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[sdog4127]

No it wouldn't.

 

4hi locks the front and rear together

 

4auto does not

 

It's ok not to know the answer....you can just say I don't know

 

We just need someone who knows more about the systems than you or I

 

 

 

Gentlemen. Former Master auto tech and I have worked on the GM AutoTrac many times. It's an extremely simple system:

 

The transfer case uses clutches and a mechanical force motor to apply varying pressure to the clutch plates connecting to the front driveshaft.

 

The clutch has preload on it, which means the front driveshaft is always engaged and turning the front differential. If you go under your truck, you will find that you cannot turn your front driveshaft freely. (With enough pressure it can slip, but this would mean your clutches are probably wearing out).

 

So since your front diff is always spinning, it is at the correct speed when you engage 4A or 4Hi. When you shift into 4A or Hi there is an actuator on the front axle that locks the front axle to the differential carrier so the front wheels are then mechanically locked in to the power train.

 

The auto feature then works by monitoring input and output speed of the transfer case. It continuously adjusts pressure to the clutch pack in the transfer case to maintain no or a small percentage of slip. Because the clutch is preloaded and always has a little pressure on it, it takes milliseconds to add power to the front axle when slip is detected. This is why the system reacts so fast. You should never feel a delay in the front kicking in when in auto. If there is a delay, you have worn parts in the transfer case.

 

4Hi works similar, except the force (shift) motor on the transfer case simply applies high pressure at all times to the clutch not allowing any slip. There may be an actual mechanical connection in 4Hi but I can't say for sure. But I do know the clutch pack controls the auto feature.

I have seen many of these clutches burnt out from people using auto when they really should be in 4Hi and they put way too much torque on the front axle. They are clutches like in an auto transmission. Big difference is we only have 1.5 qts of autotrac fluid in the transfer case and it can get overheated quickly if the auto feature is used when conditions really warrant 4Hi. It is good to change the fluid frequently too, because of this.

Hope that helps explain a bit. Auto is meant to use for varying conditions, but if constant power is needed up front you will save your transfer case by using 4Hi.

 

 

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[sdeeter19555]

In nj we have intersections you have no choice.

 

You can wait there for, no exxageration, 10 minutes if you don't "thread the needle" and find an opening.

 

It's mandatory in some places.

 

All 4 of my tires provide braking, all 4 provide the ability to turn, it is no doubt safest to have all 4 accelerate.

 

I've never had an issue with 2wd in the wet until this truck, I have no idea how anybody manages in 2wd unless you live in a relaxed driving rural area. It's such a pain in the ass. I simply cannot turn and accelerate with more than 5-10% throttle. That's like most cars in the snow.

 

The goodyear sra's, an unloaded bed, an incosistant throttle, and a ton of power all conspire to make it the worst performing 2wd in the wet ever created. I've never driven anything even close as bad as this except a motorcycle with cold tires.

How do people survive with a 2wd or non-AWD?

 

I agree with some folks, it depends a lot on the tires and some OE tires suck before they are installed on the rim.

 

Keep in mind, I drive Philly suburb traffic...not much different from Nj. My 2500 is a daily driver...auto 4wd isn't an option on my low-buck model.

 

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[truckguy82]

Gentlemen. Former Master auto tech and I have worked on the GM AutoTrac many times. It's an extremely simple system:

 

The transfer case uses clutches and a mechanical force motor to apply varying pressure to the clutch plates connecting to the front driveshaft.

 

The clutch has preload on it, which means the front driveshaft is always engaged and turning the front differential. If you go under your truck, you will find that you cannot turn your front driveshaft freely. (With enough pressure it can slip, but this would mean your clutches are probably wearing out).

 

So since your front diff is always spinning, it is at the correct speed when you engage 4A or 4Hi. When you shift into 4A or Hi there is an actuator on the front axle that locks the front axle to the differential carrier so the front wheels are then mechanically locked in to the power train.

 

The auto feature then works by monitoring input and output speed of the transfer case. It continuously adjusts pressure to the clutch pack in the transfer case to maintain no or a small percentage of slip. Because the clutch is preloaded and always has a little pressure on it, it takes milliseconds to add power to the front axle when slip is detected. This is why the system reacts so fast. You should never feel a delay in the front kicking in when in auto. If there is a delay, you have worn parts in the transfer case.

 

4Hi works similar, except the force (shift) motor on the transfer case simply applies high pressure at all times to the clutch not allowing any slip. There may be an actual mechanical connection in 4Hi but I can't say for sure. But I do know the clutch pack controls the auto feature.

I have seen many of these clutches burnt out from people using auto when they really should be in 4Hi and they put way too much torque on the front axle. They are clutches like in an auto transmission. Big difference is we only have 1.5 qts of autotrac fluid in the transfer case and it can get overheated quickly if the auto feature is used when conditions really warrant 4Hi. It is good to change the fluid frequently too, because of this.

Hope that helps explain a bit. Auto is meant to use for varying conditions, but if constant power is needed up front you will save your transfer case by using 4Hi.

 

 

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Awesome info, so it doesn't lock the front in auto!

 

Would you say you are harming the system at all if you are leaving it in 4auto during wet conditions?

 

What about leaving it in 4auto 24/7?

 

Would you say it's almost exactly like an awd system? I mean your saying that you shouldn't use it when conditions really call for 4wd because of the slipping between the front and rear. This is exactly what my awd system in my acura does. If I abuse it, the diff fluid overheats, I know because I had a warning pop up. (I had the fluid changed after)

 

It almost sounds like it operates exactly like an awd system from your description, which is obviously safe to use 24/7 because you don't have a choice lol.

[truckguy82]

How do people survive with a 2wd or non-AWD?

 

I agree with some folks, it depends a lot on the tires and some OE tires suck before they are installed on the rim.

 

Keep in mind, I drive Philly suburb traffic...not much different from Nj. My 2500 is a daily driver...auto 4wd isn't an option on my low-buck model.

 

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Yup philly suburbs of nj

 

My previous truck, a tahoe, I would never want or consider 4wd in the wet.

 

Your 2500 is likely far better than my truck in the wet. It weighs more, has less power, and a beefier/heavier drivetrain which makes it less "touchy"

 

I've never once had a problem driving in the wet with any 2wd vehicle until this one. It's aweful. Can't wait until I need replacement tires.

[kstruckcountry]

Gentlemen. Former Master auto tech and I have worked on the GM AutoTrac many times. It's an extremely simple system:

 

The transfer case uses clutches and a mechanical force motor to apply varying pressure to the clutch plates connecting to the front driveshaft.

 

The clutch has preload on it, which means the front driveshaft is always engaged and turning the front differential. If you go under your truck, you will find that you cannot turn your front driveshaft freely. (With enough pressure it can slip, but this would mean your clutches are probably wearing out).

 

So since your front diff is always spinning, it is at the correct speed when you engage 4A or 4Hi. When you shift into 4A or Hi there is an actuator on the front axle that locks the front axle to the differential carrier so the front wheels are then mechanically locked in to the power train.

 

The auto feature then works by monitoring input and output speed of the transfer case. It continuously adjusts pressure to the clutch pack in the transfer case to maintain no or a small percentage of slip. Because the clutch is preloaded and always has a little pressure on it, it takes milliseconds to add power to the front axle when slip is detected. This is why the system reacts so fast. You should never feel a delay in the front kicking in when in auto. If there is a delay, you have worn parts in the transfer case.

 

4Hi works similar, except the force (shift) motor on the transfer case simply applies high pressure at all times to the clutch not allowing any slip. There may be an actual mechanical connection in 4Hi but I can't say for sure. But I do know the clutch pack controls the auto feature.

I have seen many of these clutches burnt out from people using auto when they really should be in 4Hi and they put way too much torque on the front axle. They are clutches like in an auto transmission. Big difference is we only have 1.5 qts of autotrac fluid in the transfer case and it can get overheated quickly if the auto feature is used when conditions really warrant 4Hi. It is good to change the fluid frequently too, because of this.

Hope that helps explain a bit. Auto is meant to use for varying conditions, but if constant power is needed up front you will save your transfer case by using 4Hi.

 

 

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I think it's worth noting that the front axle IS disengaged in 2hi, and is engaged in Auto4... Great explanation.

 

And it's very different from AWD because AWD generally has a preset torque bias that is in effect 100% of the time, where the auto system can be deactivated. The mechanicals are vastly different as well.

 

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[sdog4127]

Awesome info, so it doesn't lock the front in auto!

 

Would you say you are harming the system at all if you are leaving it in 4auto during wet conditions?

 

What about leaving it in 4auto 24/7?

 

Would you say it's almost exactly like an awd system? I mean your saying that you shouldn't use it when conditions really call for 4wd because of the slipping between the front and rear. This is exactly what my awd system in my acura does. If I abuse it, the diff fluid overheats, I know because I had a warning pop up. (I had the fluid changed after)

 

It almost sounds like it operates exactly like an awd system from your description, which is obviously safe to use 24/7 because you don't have a choice lol.

 

AWD systems are usually mechanically connected all the time and have s differential between front and real axles instead of s transfer case. This continuously splits power from front to rear just like a rear differential splits power to the left and right wheel. Additional features have been added over the years by applying brakes and having clutches at every output to control power distribution, but that is AWD in its most basic form.

 

The question if you can use auto all the time is subjective. I would say no. If there is no big chance of traction loss you are keeping the front differential "locked in" for no reason and will experience some economy loss as well as unnecessary wear on the system, albeit not much if there is no slippage. But every time you make a turn on dry pavement the clutches in the transfer case need to slip because the front axle is locked. This is unnecessary tire and transfer case wear in my opinion. You will notice in auto the steering doesn't bind up on dry pavement. This is because the clutches are allowing slippage. In 4Hi you will jump all over the place because it doesn't allow slippage.

 

My opinion is I have autoTrac so I will use it. You shouldn't be afraid to break it, just understand how it works and you won't get into trouble! If you are off round and climbing hills it doesn't make sense to put all that stress on the clutches dice they are continuously adjusting for slip. Use 4HI. Any driving around town or on the highway when conditions are changing continuously, that is what auto is for. It is a comfort feature. Just make sure to change the fluid once and awhile [emoji41].

 

 

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[Havvkeye]

Yup philly suburbs of nj

 

My previous truck, a tahoe, I would never want or consider 4wd in the wet.

 

Your 2500 is likely far better than my truck in the wet. It weighs more, has less power, and a beefier/heavier drivetrain which makes it less "touchy"

 

I've never once had a problem driving in the wet with any 2wd vehicle until this one. It's aweful. Can't wait until I need replacement tires.

 

Sounds like you already do need replacement tires...

[Sean Neilan]

In nj we have intersections you have no choice.

 

You can wait there for, no exxageration, 10 minutes if you don't "thread the needle" and find an opening.

 

It's mandatory in some places.

 

All 4 of my tires provide braking, all 4 provide the ability to turn, it is no doubt safest to have all 4 accelerate.

 

I've never had an issue with 2wd in the wet until this truck, I have no idea how anybody manages in 2wd unless you live in a relaxed driving rural area. It's such a pain in the ass. I simply cannot turn and accelerate with more than 5-10% throttle. That's like most cars in the snow.

 

The goodyear sra's, an unloaded bed, an incosistant throttle, and a ton of power all conspire to make it the worst performing 2wd in the wet ever created. I've never driven anything even close as bad as this except a motorcycle with cold tires.

I live in Long Island. Never once used auto4 in rain or even snow. This truck handles worlds better than my old 95 S10 did. I also have the SR-A tires.

[Bowhunt24]

I use auto 4 quite a bit. I have the lower gear rear end for towing and the crap stock tires still so getting out of my steep driveway or pulling out into traffic when it is very rainy out is tough w/o popping it into auto. You def lose a few miles per gallon if you leave it on.

 

I'm hoping a new pair of AT style tires will make it so I don't have to go back and forth, but for now it works and has no issues. I also have my wife put it in auto when very rainy and she is driving. Not a ton of experience with trucks/rear wheel drive so it is helpful for her.

[TxTruckMan]

 

Me too.

 

Those of you who think you need 4 auto in the rain to pull out of a driveway are forgetting one lesson from driver's ed: YOU need to adjust your driving for the conditions. If you can't pull out without spinning your tires, YOU are giving it too much throttle, or your tires are bald. Both are problems that you should correct. if you need to peel out to pull out into traffic, it sounds like you don't have a large enough gap to safely proceed. I know some areas have a lot of traffic, so maybe you need to wait longer until the light turns red up the road. Yea traffic sucks, but you can't drive like you're in a race-car if the road is wet and there is heavy traffic anyway.

"Adjusting to conditions" doesn't just mean lightening up on the throttle. It's "all of the above". Using AUTO is adjusting to the conditions. Turning your windshield wipers on in the rain is adjusting to the conditions. Using snow tires in the winter is adjusting to the conditions. Turning your headlights on at night is adjusting to conditions. None of those items are mandatory for driving, but they sure make it a hell of a lot easier.

 

So no, it's not 100% necessary to use AUTO in the rain, but I can promise you that it's 200% easier to drive with AUTO in the rain over 2wd. This is my first truck in 20 years of truck ownership to have AUTO and I can tell you that it's a great addition. I would equate it to the advent of anti-lock brakes (another feature that's not needed but sure saves your butt in the rain).

 

So, if you two know-it-alls want to ignore a great driving aid on your trucks - go for it. But please stop trying to convince others that it's dumb to use AUTO in the rain. YOU ARE WRONG.

 

Of course a wet road has less traction than a dry road. But, I'm just saying the same thing I said in the other thread, that auto4 in the rain is overkill in my opinion and it's not using it as it was designed. Think about this. Stop at the very bottom of a steep hill while it's raining. then try to go up it. You won't have any trouble getting up the hill even though it's less traction than on dry pavement. Then do the same thing on a snow covered road. You either will have to have it in 4 or it will be very hard in 2wd. I just don't think a wet road is enough of a traction loss to use auto4.

You posted earlier that you had no problem admitting when you're wrong. sdog4127 said that you're wrong. Can you admit it?