Purpose of 4WD auto if you have to use gas?

[redvettx2]

My truck doesn't have it but I have had rigs that do. I think it works great when it not bad enough to run 4wd but it is still slick in spot, over passes etc. If it senses the rear tires slipping it engages the front drive shaft. Not complex but great for highway running and its icy in spots. I ran with it when with it when it bad too. Full time 4wd burns lots of fuel. I can get most places in 2wd so auto works great as it is there when you need it but 98% of the time your still in 2wd and efficient.

 

[corneileous]

I believe if you are in any 4wd mode you will not have ABS. so i will drive 2wd always unless i NEED 4wd

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ABS is not turned off in 4WD
You can turn off the traction control and vehicle stability control (which turns back on at 40mph wheel speed).

Your ABS should only turn off while in 4-LO.




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[crash68]

Your ABS should only turn off while in 4-LO.

Antilock Braking System (ABS) is different from Traction Control or Vehicle Stability Control.
ABS is always active unless you pull the fuse, it doesn't turn off just cause your in 4X4

 

[corneileous]

Antilock Braking System (ABS) is different from Traction Control or Vehicle Stability Control.
ABS is always active unless you pull the fuse, it doesn't turn off just cause your in 4X4

Guess I’ll have to look this weekend on my new truck to see what it does but I’m pretty sure that on my old 08, that when you put it in 4-LO- not just any 4WD mode, the display said ESP and ABS was disabled.


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[huntergreen]

My truck doesn't have it but I have had rigs that do. I think it works great when it not bad enough to run 4wd but it is still slick in spot, over passes etc. If it senses the rear tires slipping it engages the front drive shaft. Not complex but great for highway running and its icy in spots. I ran with it when with it when it bad too. Full time 4wd burns lots of fuel. I can get most places in 2wd so auto works great as it is there when you need it but 98% of the time your still in 2wd and efficient.

I have that 4auto takes a chunk out of mpg.

 

[Fatbob Frank]

I work 3rd shift so I'm always on the road hours after they've pulled the plows off and have driven to work in damn rotten conditions.
My experience is:
1. If I think I might need 4wd, I put it in 4high.
I never bother with 4auto.
I might lose 1-2 mpgs but it's a lot cheaper than missing work cause I'm in the ditch and tow truck bills aren't cheap either.
2. Any 4wd, (jeep, truck or SUV) is only as good as the tires you put on it.

 

[Krein]

Thats why your truck comes with a 4wd high option, like Fatbob Frank said if 4wd is needed then just use 4high

 

[corneileous]

I work 3rd shift so I'm always on the road hours after they've pulled the plows off and have driven to work in damn rotten conditions.
My experience is:
1. If I think I might need 4wd, I put it in 4high.
I never bother with 4auto.
I might lose 1-2 mpgs but it's a lot cheaper than missing work cause I'm in the ditch and tow truck bills aren't cheap either.
2. Any 4wd, (jeep, truck or SUV) is only as good as the tires you put on it.

If the roads are that bad, you’re probably better off in 4HI anyway, than Auto. I think auto is only really for the roads not being too bad. But keep in mind, due to the nature and design of these auto transfer cases, even in 4HI-lock, and even in 4-LO, they aren’t in a full time four-wheel drive.

If the roads are bad enough to justify full time 4WD, no one’s worried about losing gas mileage. The only reason for that talk was in response to driving in virtually non-slippery conditions with the transfer case in 4WD Auto. When you’re only in 2-wheel, the front part of the drivetrain is how it always has been. Axle shafts only.... are turning with the front wheels. When Auto is engaged, the front diff is now fully locked, along with the front driveline, creating a lot more drag, but there is no power going to the front due to the clutch pack system in the transfer case.

But yes, tires do make a difference in a 4x4 but the thing that gets a lot of people the most, is over confidence. Back in my 20 year span in south-western Colorado, the majority of the people off in the ditch when the roads got slick was the fools with four wheel drives that thought they were invincible and could drive as fast as they wanted too...lol.


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[Sportznut]

For me the biggest advantage to 4WD (aside from getting unstuck) is when you are headed toward that tree and you have the confidence to turn the wheel and give the pedal a decent push to get you headed in the right direction.



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[CostaRam]

I work 3rd shift so I'm always on the road hours after they've pulled the plows off and have driven to work in damn rotten conditions.
My experience is:
1. If I think I might need 4wd, I put it in 4high.
I never bother with 4auto.
I might lose 1-2 mpgs but it's a lot cheaper than missing work cause I'm in the ditch and tow truck bills aren't cheap either.
2. Any 4wd, (jeep, truck or SUV) is only as good as the tires you put on it.

Wise words of someone who knows his s@#t!

Chris

 

[indept]

If the roads are bad enough to justify full time 4WD, no one’s worried about losing gas mileage. The only reason for that talk was in response to driving in virtually non-slippery conditions with the transfer case in 4WD Auto. When you’re only in 2-wheel, the front part of the drivetrain is how it always has been. Axle shafts only.... are turning with the front wheels. When Auto is engaged, the front diff is now fully locked, along with the front driveline, creating a lot more drag, but there is no power going to the front due to the clutch pack system in the transfer case.

Is that making much difference? When in 2wd the front axles are still turning the front diffs ring gear which is still mated to the pinion gear which is still turning the driveshaft from the transfer case to the front diff so while the front wheels aren't being driven their weight (and any drag associated) is still being turned so how much is 4wd vs 2wd costing in mpg. Can't be enough to worry about.

Is there a clutch or shift mechanism on the front diff to engage or disengage it? I haven't bothered to look but thought only the transfer case is engageable.

 

[chrisbh17]

Is that making much difference? When in 2wd the front axles are still turning the front diffs ring gear which is still mated to the pinion gear which is still turning the driveshaft from the transfer case to the front diff so while the front wheels aren't being driven their weight (and any drag associated) is still being turned so how much is 4wd vs 2wd costing in mpg. Can't be enough to worry about.

Is there a clutch or shift mechanism on the front diff to engage or disengage it? I haven't bothered to look but thought only the transfer case is engageable.

The front axle actuator is there to link the right front axle into the diff. The left front axle, like you said, is always connected to part of the diff and "back feeding" the front driveshaft (i.e. it always spins, even in 2WD).

The real test would be to pull the front driveshaft off and drive the truck, noting mpg. A large mpg difference would indicate there is enough drag to make a difference. My guess is that the data would be within a margin of error, or maybe 1mpg or something.

 

[corneileous]

Is that making much difference? When in 2wd the front axles are still turning the front diffs ring gear which is still mated to the pinion gear which is still turning the driveshaft from the transfer case to the front diff so while the front wheels aren't being driven their weight (and any drag associated) is still being turned so how much is 4wd vs 2wd costing in mpg. Can't be enough to worry about.

Is there a clutch or shift mechanism on the front diff to engage or disengage it? I haven't bothered to look but thought only the transfer case is engageable.

As far as I know, when these newer trucks with these newer automatic transfer cases are in 2-wheel(not 4-Auto), they’re the same as they’ve always been in the past, where everything in the front axle is turning except for the front driveline. When you put it In 4-auto, it locks In the front diff which in turn locks in the front drive shaft, but there’s no power connection to the front driveline in the transfer case so if you think about it, you’re having everything from the front drive shaft to the axle U joints that’s being driven by the front wheels. That’s quite a bit of drag.

But you’re right, it’s probably not costing you that much anyway, considering that even when in straight-up 2WD, you still have everything up front turning off the front wheels minus the drive line.

But if I’m not mistaken, there’s a clutch pack there in the transfer case where the front drive attaches to the output shaft of the transfer case, or there’s a clutch pack on the big sprocket where the big chain runs over to, to power the front wheels.


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[redline1983]

if you actually need 4wd - then put it in 4wd lock. Its a great option for those in between periods.

 

[indept]

if you actually need 4wd - then put it in 4wd lock. Its a great option for those in between periods.

What if they're post-menopausal...

 

[Fatbob Frank]

During the winter my truck spends more time in 4Hi than out.
Cause this....

 

[ProjectWolf]

sigh... 4 wheel drive does NOT MEAN 4 WHEEL STOP. To the original posters concern, having a truck that can move in snow does absolutely nothing when it comes to stopping in snow, or changing direction in snow. Whether the truck is in 2wd mode or 4, you hitting the gas has nothing to do with your ability to stop. That depends entirely on the tires having traction, and the braking system performing well. I have lived in New England my entire life, I have driven every kind of vehicle in the snow from drift cars, fwd, rwd, 4wd, and awd. If you are concerned with actually moving in snow, your tires are the defining difference along with driver skill. ********* driving 4wd or awd vehicles have crashed more in snowstorms than 2wd cars because people are too stupid to drive intelligently because they think "I have 4wd"

 

[corneileous]

sigh... 4 wheel drive does NOT MEAN 4 WHEEL STOP. To the original posters concern, having a truck that can move in snow does absolutely nothing when it comes to stopping in snow, or changing direction in snow. Whether the truck is in 2wd mode or 4, you hitting the gas has nothing to do with your ability to stop. That depends entirely on the tires having traction, and the braking system performing well. I have lived in New England my entire life, I have driven every kind of vehicle in the snow from drift cars, fwd, rwd, 4wd, and awd. If you are concerned with actually moving in snow, your tires are the defining difference along with driver skill. ********* driving 4wd or awd vehicles have crashed more in snowstorms than 2wd cars because people are too stupid to drive intelligently because they think "I have 4wd"

Correctomundo.....

Of course, driving in 4-wheel isn’t always a recipe for disaster if you drive with caution, keep adequate space, slow down slower for stops and curves- and most definitely don’t drive like you think that 4-wheel drive is making you superdriver.


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[indept]

Bottom line is that for everyday drive to work situations I find 4wd auto works fine and when it snows 4wd hi does a good job keeping me moving. As you have pointed out stopping is a different story.... Tires tires tires