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Driving in 4wd


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We are currently experiencing icy roads in N. Texas and I've had to engage the 4wd on my 2014 Z71. My question is this, how fast can I drive while in 4wd (auto)? The highways are iced over, but there are some long stretches of road that have been cleared off where one can drive 55mph. Thanks in advance for your help.

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I used mine for the first time today here in Michigan with 4 inches of snow and it works great! Interesting thing I noticed is that it runs in V4 mode much quicker and stays in it longer....This truck is too smart for me!

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Yeah but what happens if it engages @ 70mph? That can't be good for the truck. Or, what if it senses slippage at low speed while turning say, then you're pulling onto dry pavement - running in 4WD while turning on dry pavement is bad news, even if its in the middle of switching back/forth.

 

I just don't trust 4wd auto period...maybe I'm being too "old school", but I run snow tires, only time I'll use 4wd is if it is snow/mud/slush COVERED roads or if I'm literally off roading, and then I'll put it in 4WD hi. If you're in a situation where you need 4WD LO you're in the wrong vehicle to begin w/ IMO haha

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Why would it engage at 70? If you're driving 70 on ice you need to rethink your life. Turning tight in 4wd won't hurt anything. The front diff is an open diff.

 

I have a similar system in my 2006 and haven't had any mechanical troubles yet.

 

The fastest I have used auto 4x4 is 55, like I said I wouldn't be driving faster than that in sketchy conditions anyways. But I know people who have left it in on accident for a few weeks and haven't had any issues. It's a great system IMO. I don't need it often but when I do it's great.

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I've had auto in 4 different vehicles now. '98 S10 Blazer, '02 Avalanche, '07 Yukon, and '14 Sierra (well, sort of, more on that in a minute)

 

The Auto setting is SLICK.

 

Having lived in NoDak and Northern Minn, all of those vehicles got plenty of winter driving in plenty of crappy conditions. Typically, I've left them in Auto throughout winter except during those stretches where we haven't had snow and the roads are clean. That includes going 70-80 on the interstate and in bad conditions - and I have had it kick in at 70 mph. From what I've always understood, having the auto kick in is not truly the same as driving constantly in 4 wheel.

 

My Yukon did start to get 'service 4 wheel drive' messages, but it always worked and I'm not surprised to get those kind of messages at 150K miles.

 

My Avalanche would catch a little doing a tight turn in 4wheel even at low low speed, but never had it do that while in auto (probably wasn't engaged). The Yukon would also catch a bit on a tight turn.

 

S10 performed flawlessly with Auto.

 

That all being said, I took my first long trip with the Sierra this weekend and put miles #450-#670 on it... Leaving town I had it in Auto (and needed it) but while driving around the cities I had a tough time, assumed it was the tires, but finally realized Auto & 4 wheel are not working at all. I'm not getting the 'Service 4 Wheel' message.

 

I'm going to be talking to the dealership today, don't know when they'll be able to get it in though. I'll chat with them about the Auto setting and their thoughts on when/how it should be used...

 

Why would it engage at 70? If you're driving 70 on ice you need to rethink your life.

 

I drove back on the interstate yesterday with my Auto & 4wh not working...there are times, up here at least, where you can be driving 70 on the interstate on dry pavement and unexpectedly hit black ice or a section of pack ice where having the Auto engage the front wheels is a really really nice feature.


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Auto 4wd can be driven at normal speeds. But if you are hoping its going to save your butt while driving 70 mph on the highway think again. If you catch some ice at that speed, regardless of being in 4wd or 2wd, the truck is gonna lose control.

 

 

When I had my 68 bronco if you turned the wheels too hard in 4wd it would kind of chug till the wheels straightened out. I used to hate getting out and turning the locking hubs on.

 

These trucks arent your 68 Bronco, 4wd technology has improved in the past 40 years....

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I put it in 4WD HI just to see what its like and on dry pavement the truck was lurching while turning. I guess w/ the auto setting it wouldn't do that, I'm happy I got snow tires anyhow as I always say sure, you can get moving in the snow/ice/sleet w/ 4WD no problem, but when it comes to stopping/turning/maneuvering its night and day on the snows.

 

I am anxious to head up to ski country this year running the snows & 4WD to see how well this rig handles it. I'm assuming will be pretty much "unstoppable" w/ a full tank of gas to add weight to the rear.

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It will do awesome with snow tires. The burb we take has Michelin LTX and it's a beast on snowpack. My truck did ok with the crappy Goodyears, but from the little bit we've had the Cooper's I have now (M&S rated) aren't even real snow tires and they're awesome. With actual snow tires it would be on rails.

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The auto setting engages the front diff and the front plates by about 10% from what I read, then once the system senses slippage it locks the front diff instantly to engage the front system.

 

you can drive Auto and 4wd Hi at any speeds with no harm. No different than an AWD system that some cars use.

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Why would it engage at 70? If you're driving 70 on ice you need to rethink your life. Turning tight in 4wd won't hurt anything. The front diff is an open diff.

 

I have a similar system in my 2006 and haven't had any mechanical troubles yet.

 

The fastest I have used auto 4x4 is 55, like I said I wouldn't be driving faster than that in sketchy conditions anyways. But I know people who have left it in on accident for a few weeks and haven't had any issues. It's a great system IMO. I don't need it often but when I do it's great.

If you turn on dry pavement in 4WD you will wreck something eventually. OP, you are fine leaving your truck in 4wd Auto. The speed will not hurt it at all. Auto 4wd works by engaging clutches in the transfer case. When it detects slip it engages the clutches and releases them when there is no slip. BTW, in the GMT900 the auto 4wd works very seamlessly.

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