Slipping or stuttering in 4wd auto mode -- is this normal?

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WillCO

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I have never read that, everyone else I have seen posting in similar threads about 4x4 Auto always states that "it is not designed to be used full time but only during times of unknown road conditions that vary between slick and dry."

Although I know people who leave it in 4x4 auto full time regardless.

I leave mine in 2-HI but for the first 34,000 miles I didn't own it I have no idea how it was used.
The difference would be that I posted text from the actual GM owners documentation and you've been reading chat board posts by, well...whomever.

Vive l'internet.
 

Sam Harris

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I use my 4wd Auto in rain storms out here in Texas. When I was in Colorado, I’d just use 4Hi if I was concerned about slipping around too much in the snow.
 

Larryjb

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I believe that many AWD systems use a fluid couple between front and rear, whereas the Tahoe is a mechanical couple activated with clutches. That would explain why you are able to drive other AWD systems without feeling the jumping around.
 

Sam Harris

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I believe that many AWD systems use a fluid couple between front and rear, whereas the Tahoe is a mechanical couple activated with clutches. That would explain why you are able to drive other AWD systems without feeling the jumping around.
As well, the AWD systems have the functionality of adjusting slippage on the fly, as in a certain amount of torque to each wheel, while with our auto 4wd, it just engages and disengages the front wheels entirely. (AFAIK)
 

BlaineBug

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The difference would be that I posted text from the actual GM owners documentation and you've been reading chat board posts by, well...whomever.

Vive l'internet.
I understand that totally. Previously I have described auto-4wd as a "full time all wheel drive" system, personally. Isn't it nearly identical? A lot of the older generation GM full size SUVs had no ability to select 2wd and were constantly in 4x4. My Wife's Nissan Rogue also has full time 4wd with the ability to "4x4 lock" at the press of a button, and my Father's 2003 Element had full time AWD with no selections to make whatsoever (sold that in 2016.) I assume these full time AWD systems use clutches in their transfer cases just like GM does when you use "auto 4x4" mode.
 

WillCO

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I understand that totally. Previously I have described auto-4wd as a "full time all wheel drive" system, personally. Isn't it nearly identical? A lot of the older generation GM full size SUVs had no ability to select 2wd and were constantly in 4x4. My Wife's Nissan Rogue also has full time 4wd with the ability to "4x4 lock" at the press of a button, and my Father's 2003 Element had full time AWD with no selections to make whatsoever (sold that in 2016.) I assume these full time AWD systems use clutches in their transfer cases just like GM does when you use "auto 4x4" mode.
Snarkiness aside, I can objectively see how a mechanical differential that activates the front axle based on slippage at the rear would be engaging and disengaging the front differential a lot more often than a dedicated AWD system that always has it engaged at some level. In the same way as flipping the light switch causes a lot more wear on the light bulb than having the light on does, this approach could wear the system prematurely.

It makes sense. Question is whether it's material, and more specifically whether the impact of the wear is material enough to offset the disadvantage of having to activate the AWD when you feel you need it, or if you forget.

Long ago I had one of those Mitsubishi Montero Sport SUVs that had a manual 4WD differential. To activate 4WD I had to reach down and shift a lever (though at least I didn't have to get out and lock the wheels). One time I was driving along the highway after a freeze in 2WD, hit some ice, and ended up piling the thing up against the guardrail. The world will never know whether or not having the front axle driven might have kept me from spinning out completely because I didn't think to have 4WD on at that moment.
 

Geotrash

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Long ago I had one of those Mitsubishi Montero Sport SUVs that had a manual 4WD differential. To activate 4WD I had to reach down and shift a lever (though at least I didn't have to get out and lock the wheels). One time I was driving along the highway after a freeze in 2WD, hit some ice, and ended up piling the thing up against the guardrail. The world will never know whether or not having the front axle driven might have kept me from spinning out completely because I didn't think to have 4WD on at that moment.
With a 4wd SUV running in 2WD mode without traction control in variable icy conditions, when that backend breaks loose, it can be nearly uncontrollable. I had a '99 Isuzu Rodeo that scared us silly on wintry roads a handful of times until I got in the habit of putting into 4WD when the roads got slippery.
 

WillCO

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With a 4wd SUV running in 2WD mode without traction control in variable icy conditions, when that backend breaks loose, it can be nearly uncontrollable. I had a '99 Isuzu Rodeo that scared us silly on wintry roads a handful of times until I got in the habit of putting into 4WD when the roads got slippery.
It's safe to say that experience changed me forever as a driver. Whenever I see people driving like morons on slick roads, now I always think "ah, you haven't had your accident yet."

I was actually on my way from Denver to Colorado Springs to make a sales presentation. After the wreck the truck was still drivable, I actually continued and did the meeting.
 

Larryjb

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A long long long time ago, we had to get out and lock hubs to use 4WD.

Then came along automatic hubs, but you still had to lock them for full time 4WD.

Sometimes they'd get stuck in the locked position and we'd have to drive backwards for a few feet to be able to unlock them. In bad cases, we had to jack up the wheels to release the tension to be able to unlock them.

The AWD systems (on our Explorer) are good for my wife, so she doesn't need to think about it.
 

BlaineBug

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Snarkiness aside, I can objectively see how a mechanical differential that activates the front axle based on slippage at the rear would be engaging and disengaging the front differential a lot more often than a dedicated AWD system that always has it engaged at some level. In the same way as flipping the light switch causes a lot more wear on the light bulb than having the light on does, this approach could wear the system prematurely.

It makes sense. Question is whether it's material, and more specifically whether the impact of the wear is material enough to offset the disadvantage of having to activate the AWD when you feel you need it, or if you forget.

Long ago I had one of those Mitsubishi Montero Sport SUVs that had a manual 4WD differential. To activate 4WD I had to reach down and shift a lever (though at least I didn't have to get out and lock the wheels). One time I was driving along the highway after a freeze in 2WD, hit some ice, and ended up piling the thing up against the guardrail. The world will never know whether or not having the front axle driven might have kept me from spinning out completely because I didn't think to have 4WD on at that moment.

I also owned a 1995 Jeep Cherokee from 2005-2011 with a manually activated lever actuated 4x4 NP231 transfer case with 2hi, 4 hi, 4 lo, and neutral. Some Jeeps also came with a NP242 I believe it was called which had all of the same functions but also had a full time 4x4. One of my friends had a 1997 Jeep Grand Cherokee which had a full time 4x4 transfer case which still allowed you to shift into neutral or 4x4 LOW but had no ability to shift into 2 wheel drive mode. Whatever the model of that transfer case was had the tendency to fry the clutches (especially on 33's, quite a bit larger than the stock tire size,) and he had to replace his transfer case multiple times - however, when it fried the clutches, you always ended up with rear wheel drive versus no wheel drive! (or maybe it was front wheel drive? I don't remember, that was a long time ago!)
 

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