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Auto vs 2WD - MPG Question


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It’s probably not a huge difference but it stands to reason that when in “auto” there is more drag (and wear). The axle shafts and front driveshaft are spinning in auto, everything is engaged and waiting for torque from the transfer case clutch.

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On a tangent, I leave it in 2WD unless I need 4.  Guess I'm old school but on my older trucks, I'd leave the hubs (manual) unlocked until the moment 2WD failed me.

 

That said, maybe I'll give "auto" a try this weekend when we're supposed to see some snow

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9 minutes ago, Rob Mugs said:

On a tangent, I leave it in 2WD unless I need 4.  Guess I'm old school but on my older trucks, I'd leave the hubs (manual) unlocked until the moment 2WD failed me.

 

That said, maybe I'll give "auto" a try this weekend when we're supposed to see some snow

Auto is perfect for light snow/ sloppy roads with mixed snow cover. I rarely even use 4 high.
 

Auto does allow some brief slip at first and you can still spin a bit, but you’ll never really get stuck unless it’s some nasty stuff.


Auto 4x4 is also my default drag race / gap the car alongside of me at a stoplight mode. 

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On a tangent, I leave it in 2WD unless I need 4.  Guess I'm old school but on my older trucks, I'd leave the hubs (manual) unlocked until the moment 2WD failed me.

 

That said, maybe I'll give "auto" a try this weekend when we're supposed to see some snow

I used to be like that. Then a semi changed lanes and ran me into the median. It was a nightmare getting to the hubs in the deep snow. Once I did I was able to back right out. I left then locked in winter weather after that until trucks with hubs went awry.

 

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14 hours ago, OnTheReel said:

Auto 4x4 is also my default drag race / gap the car alongside of me at a stoplight mode. 

Why not toss in 4 High for that?  Seems like it'd be just a little more slippage and more wear on the clutch.  It's only like 3-4 seconds to swap between.

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48 minutes ago, Rob Mugs said:

Why not toss in 4 High for that?  Seems like it'd be just a little more slippage and more wear on the clutch.  It's only like 3-4 seconds to swap between.

Eh, I’ve tested 0-60 a bunch in each mode. There’s no appreciable difference in times, get little-to-no wheel spin in either mode. For street fun especially, I just like auto. Can steer without fear, lol.

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14 minutes ago, OnTheReel said:

Eh, I’ve tested 0-60 a bunch in each mode. There’s no appreciable difference in times, get little-to-no wheel spin in either mode. For street fun especially, I just like auto. Can steer without fear, lol.

LOL.. touche

 

I have made the mistake of forgetting to turn it off and then get the dreaded... "noooo ... I don't wanna turn"

 

Took it up to GLD for a few bone-stock passes.  Hit a 14 flat but I think a ton of that is due to the speed cap at 98.  FWIW, I also brake torqued a few passes and then just stabbed it.  Stabbing knocked 2 tenths off

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Eh, I’ve tested 0-60 a bunch in each mode. There’s no appreciable difference in times, get little-to-no wheel spin in either mode. For street fun especially, I just like auto. Can steer without fear, lol.
And with the clutch slip there is less chance of the front tires bending the tie rods and going full toe in. I know these trucks really don't have the power to do that easily but it can happen. It's common on Duramax powered trucks. Plus when crossing the slick crosswalk lines all the power going to the front end could break something. It's not as heavy duty as it's not intended to be the only one operating.

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LOL.. touche
 
I have made the mistake of forgetting to turn it off and then get the dreaded... "noooo ... I don't wanna turn"
 
Took it up to GLD for a few bone-stock passes.  Hit a 14 flat but I think a ton of that is due to the speed cap at 98.  FWIW, I also brake torqued a few passes and then just stabbed it.  Stabbing knocked 2 tenths off
I was crossing the mountains in Southern Oregon and Northern California a few years ago. It was snowing hard. I was towing my travel trailer with my Duramax. The CHP chain enforcement check point made me chain up the trailer. Not the truck because it's 4WD. Just the trailer. Even though it has BF Goodrich all terrain TAs on it. I was not happy about it. When I stopped to take them off I forgot to take it out of 4WD. I didn't notice it until I got to LA. It was jumping trying to turn backing into the RV spot. As best I can tell it didn't hurt anything. Mostly freeway and it was raining hard the whole time.

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