Looking at a used 2005 half ton Chevy. It has push button 4wd.

There is the top button labeled "Auto 4x4"

What does it do and is it any good? When or why would I use it?

The button is great and probably the toughest part of the 4x4 system.

It electronically decides when you need 4x4 based on a computer's assessment of traction at any given moment. Most of the ranchers that I know that have that option run their pickups and SUVs in Auto 4x4 all the time. One guy told me that his Land Cruiser "lives in Auto 4x4". These are guys that live far from the pavement. I tend to use it only occasionally in the winter or in monsoonal rain storms. I have had it on the last three 4x4 GMC pickups and admittedly used it only sporadically.

Is it "any good"? That depends a lot on where and how you drive. It's a nice option to have if your wife or kids don't use 4WD much or don't pay a lot of attention to road conditions.

One of the features I liked best on the Chevy I had.

yeah, its what mine is usually set on driving around town in the winter when its icy...

Does it flip the truck into 4High automatically, or does it somehow apply brake pressure to the slipping wheel, or does it perform some sort of locker function?

+1

Great for around town at stop signs or signals. Everybody else is churning butter and I'm humpin' to the coffee shop.

City truckin' and all..........................<grin>

The Auto 4x4 works great on my '08!! During the winter months, my truck pretty much stays in Auto 4x4.

I've been told that it puts the truck in AWD: it sends power to the other wheels when one starts slipping. 4HI locks all 4 into turning at the same rate, regardless of traction conditions, or the speed of each wheel. My understanding is that Auto 4x4 is what you should use on pavement, on account of it won't grind the tires when you're turning. Theoretically, this makes it "safer" than using 4HI, because the tires aren't made to lose traction by being forced to turn at a rate other than what the ground speed would indicate.

I've had it on 3 work trucks & 2 personal SUV's, & I like it fine. I don't know if it's a huge selling point, but it seems to work pretty well.

FC

Love the feature have it on my 2004 and it does what you just said.

throw a "usually" in front of the wont and your more correct....they will catch sometimes, but far less than in normal 4 high...it seems to me its some variation of AWD, not quite as locked up as when yah put it in normal 4 but flip a U-y on dry pavement instead of ice and your front tires will usually grind them a bit, though no where near as bad as in normal 4wd

The electronic 4WD/Auto 4WD is mechanically the same system as a manual shift 4WD. It uses a button instead of a lever to engage the front differential/4WD. It's not AWD. AWD requires a different transfer case set-up.

Auto 4WD uses the wheel speed sensors to detect slippage in the rear wheels and then automatically engages the front differential/4WD. It also automatically shifts back into 2WD thus no crow hopping or grinding the tires at low speeds on pavement.

The advantage of auto 4WD is in intermittent slippery, snowy, icy conditions on pavement where you don't want to have it locked in 4WD.

IMO, it's a very good system.


edited to add: The front tires will crow hop if it hasn't shifted into 2WD - the same as with any chevy 4WD. The front differential is the standard open dif used in all chevy trucks.

Great for winter driving.Use it all the time.

Had it on the '06 Sierra, have it on the '10 Silverado. As others have noted, generally use it on the road, whenever road conditions vary during winter driving, from some snow or ice, to light snow covered roads.

If conditions worsen and warrant it, put 'em into 4WD high. Otherwise, the "on demand" system works fine.

I can figure out when to use 4 wheel drive. I like the lever on the floor of my truck. mtmuley

I like the high beam button to be on the floor as well but good luck finding a new rig with that

That was the OP's question, hence the answers from those familiar with it.



Yeah, me too. Back when manual hubs and manually-shifted TCs were the norm. I have no problem adapting to some of the new-fangled chit offered today.

Case in point: Back when dash-mounted buttons began to appear for selecting 4WD, insisted the ol' lady order her new '94 GMC with the manual TC floor shifter, on the premise that it was one less electrical doohickus to ef up.

Didn't do any good. We had a major blizzard here in '96 and when we needed 4WD, had none. The electrical switch that locked the front axle in, took a dump during the blizzard. No manual option for that one, although eventually someone invented a manual cable aftermarket doodad to solve the problem of a bad switch.

Yep, manually-selectable stuff is great. But the OP wanted to know if auto AWD worked and what it was "good fer". It's "good fer" days when parts of the roads are bare, partially snow covered or icy in some stretches. Poke the button and drive. The system figures out when it needs to be engaged and when it doesn't, as road conditions change.

Just for the hell of it, once pushed the auto button and headed up into a steep, snow covered field in deer season. Truck moved along fairly well, but too much thrashin' to suit me, as it fought with itself as traction came and went. So naturally I just poked the 4WD high button and proceeded without any drama. That's what that option is for.

A neighbor's first 4WD vehicle was a new Chevy shortbed, '76 IIRC? Manual hubs, floor TC shifter. First snow storm that year, he headed off to the inlaws. Some snow covered roads, mostly bare. Left it in 4W high for the entire trip. Grumbled later that it sucked too much gas, couldn't turn the wheels sharply in a parking lot. Told him he could've just shifted the TC back into 2WD, put it in 4WD if it was needed. He thought that was "too much trouble".

He swapped it on a new Blazer with their then-new version of AWD.

Something we have noticed at the shop. The auto four wheel drives can cause the transfer case to start leaking. Puts some extra strain on the rear of the unit and will crack and develop a leak. Seen some at 100k to 150k with the problem.

Chris

Shifting on the '94 was controlled by a heated gas cylinder. Sometimes in real cold weather the gas wouldn't expand enough to engage 4WD, or it would take awhile. In real hot weather sometimes the heated gas wouldn't allow 4WD to disengage. And it wouldn't shift when things wore out. The factory retrofit was a solenoid which should've been there in the first place.

I have it on a 2000 GMC. I initially used it on icy roads in town, but could not tell if I needed it since I wasn't slipping anywhere. These were some real icy roads. So one morning I decided to try it without the Auto 4x4 engaged. I was slipping all over the place so turned it back on. As soon as I hit the button all slipping stopped and I had full control again.

I used it to get out of our 1/4 mile driveway in the winter at times to see how well it does. There is no difference between it and having it locked into 4x4 from what I can tell. We have it on our 2005 Suburban too. It's great when traveling highways in the wintertime.

Sounds about right? Looked it up at the time, thinking it was some sorta little "heating filament" doohickus? BTW, it was on a new Sonoma ext. cab 4x4.

Second worst part of the deal, was that the dealer was shut down for almost a week due to the blizzard, so we were "stuck" without 4WD just when we really needed it. On the brighter side, the truck actually got around fairly well in 2WD, thanks to the factory locking rear and new tires.

Thanks guys, that gives me what I needed to know.

I guess I'm the dissenter in the group. I've got a 2003 Z71 with 200,000 miles on it, and have never turned the 'auto' 4wd on. Same for my wifes 2007 Z71 with 60,000 miles. I'm either in 2wd, or 4wd. I don't really have a good reason for doing it that way, just something in my head saying I don't want it switching back and forth without me controlling it.

Getting back to this.

Cheesy

From my experiance you won't even feel it go in or out of 4wd.

Have now had two GMs with that button and have used 'em a time or two. Driving on the highway, with varying road conditions encountered (some bare, some wet, some icy and some snow covered), 'bout fits the purpose of "the button".

If'n ya want to pretend it isn't there, then don't use it?

Why someone would choose to drive under the above conditions, with the thing punched into 4WD high, or continually opting in and out of that choice, escapes me?

Yep, great when the conditions are kind of "iffy", mixed snow etc on the streets. Occasional slick spots. Off-road, I usually go with 4Hi, but also use the Auto 4x4 setting out on gravel roads if it has been wet.

Yep, good for varied road terrain. I too have heard reports of premature wear if it is left in auto all the time. I believe it locks the axle hubs but leaves the t case in 2wd. Then when slippage is detected, it can shift the t case without the delay of waiting for the hubs to lock.

I have heard it referred to as the wife button since your wife can use it and doesn't have to worry about messing anything up. That works for me.