Differences Between 4WD AUTO and 4WD HI

[Higby]

I have a 2011 Yukon XL with the Single Speed Transfer Case. Can someone give me the specific differences between Automatic Four Wheel Drive and Four Wheel Drive High? I've read people alluding to it but haven't been able to get a good understanding.

BTW thanks to everyone on this community. As a newbie I sure have gotten a lot of good information here!

 

[Donnie Yukonie]

4wd auto kinda acts like a awd vehicle when auto is selected , the vehicle remains in 2wd now when the truck senses wheel slip "spinning" the front axle automatically engages . i found Auto to work well in snow or wet grass ect... it does not hurt the vehicle to drive it around town in auto
4wd Hi means the vehicle is locked into 4wd all 4 wheels will spin . this is best used for light mud or sand ect when you need it and IMO should not be drivin around all the time in this selection only when needed

 

[jcrack_corn]

well, the above is sort of right.

the diff between 4 auto and 4 hi is all the difference in the world.

4 auto can be selected at any time (even in motion) and as mentioned above the truck will engage all wheels when needed....4 auto is meant especially for rainy conditions.

4LO is ONLY to be used off of pavement...there MUST be some slippage of the wheels (gravel, wet areas, etc) or you will trash the diff when you turn (outside wheel tries to move faster than inside wheel, but diff is locked).

4HI is like 4auto but is full time, again, not to be used on dry pavement

there is a procedure to engage and disengage 4HI/LO properly

RTFM

edit: didnt differentiate between 4hi/lo

 

[Higby]

Thanks guys. This clears things up quite a bit. The FM does not do a good job of explaining the difference. It also says that I can shift into or out of any of the 3 modes (2WD, 4WD AUTO, 4WD HI) at any speed...there is no mention of a "special procedure" so I'm interested in what you mean by that.

 

[AmazinglySmooth]

What is the difference between all of what you've described and the Denali AWD?

 

[doubletapdrew]

Denali is full time all wheel drive and controls the 4 wheels independantly.
There is no procedure shifting into or out of 4HI and can be done at any speed. If you had a 2-speed transfer case (with 4lo) that needs to be done at 3mph or less with the transmission in neutral.

 

[Donnie Yukonie]

Thanks guys. This clears things up quite a bit. The FM does not do a good job of explaining the difference. It also says that I can shift into or out of any of the 3 modes (2WD, 4WD AUTO, 4WD HI) at any speed...there is no mention of a "special procedure" so I'm interested in what you mean by that.

generally and unless tech has changed auto is shift on a fly done pretty much at any speed and in or out of drive or nuetral however to be safe NO MATTER what i always stop before putting my truck in any 4wd mode IMO
4hi can be achieved by pushing the button until the light changes modes (me i always place the truck in nuetral shift then back to drive its just what im used to)
4Lo has to be done in nuetral

 

[electro]

I had taken my transfer case out to look at the bushings and replace them on in 2000. NP 246 Transfer case or something like that.

I also added a pump bushing type thing. Basically it gave the fluid pump a little more surface area to contact when it torqued every time you apply the accelerator pedal. Over time the pump can knock against the case and eventually wear a whole through to the outside causing server fluid lose. The transfer case is made of Magnesium which can be worn down over time.

When I had the case apart or in halfs. I wasnt able to get a full understanding of out how it worked. I was however told its best to avoid 4AUTO as it basically bangs or pops into 4 wheel drive. This causes a lot of stress on particular parts which I cant name. Maybe the planetary gear system...or maybe the pin/lever that moves in and out to lock in 4 wheel drive or to disengage 4WD.

 

[doubletapdrew]

I was however told its best to avoid 4AUTO as it basically bangs or pops into 4 wheel drive. This causes a lot of stress on particular parts which I cant name. Maybe the planetary gear system...or maybe the pin/lever that moves in and out to lock in 4 wheel drive or to disengage 4WD.

I had a 02 silverado and didn't like the auto 4wd, it does feel like it pops into 4wd while the rear wheels are slipping. Can't be good.

 

[jbyrd]

Hi All, Thanks for all the info that this forum supplies, you guys/gals rock. I recently purchased a 2016 tahoe with 65K miles and experienced the same issue. The drive whines slightly while turning slightly (not the jumping actions when turning hard full) when in 4H in drier conditions. I then found this on the GM site that dives into some details. - https://www.gmc.com/gmc-life/how-to/when-to-use-four-wheel-drive. I'll be changing the transfer case fluid soon to make sure that clean as well. Is there anything else I should give some maintenance attention too? Any other lube points to consider? This truck is cherry clean, and I want to keep her top notch. Thanks in advance for any response. Jbyrd