Help me understand "auto 4wd" functions

[zidjan]

Hey guys, ever since I bought my rig i never engaged the 4wd... what's the difference between the auto 4wd and 4hi??

 

[Ice98]

What year do you have?

Mine doesn't have Auto (that was added later)

Basically, in Auto the vehicle will switch to 4wd on its own, but not until it senses that the tires are slipping, so its really a crap shoot as to when it will engage and how that will effect your driving, honestly from what I have read it seems people aren't that big of a fan of the system

4hi is a 4wd gearing that allows for a fairly fast speed of travel, where as 4lo is a lower range power distribution that is limited in the speed you can travel without damaging the vehicle

 

[zidjan]

Mine's a 1998 ... so if the road is icy it's better to put it to 4Hi as oppose to leaving it in auto 4wd? then I kept hearing people advised against driving 4hi in flat surfaces.

 

[lesterl]

Ive driven 70mph on a fresh snowpack to work 45 min away for normal weather in 4hi.

I didn't know the GMT400's had Auto 4wd, thought that started for the newer ones...

I would use 4hi or 2hi, then you don't have the computer making a decision at the wrong time and ending up spun out...

 

[Ice98]

Mine's a 1998 ... so if the road is icy it's better to put it to 4Hi as oppose to leaving it in auto 4wd? then I kept hearing people advised against driving 4hi in flat surfaces.

4Hi is fine on hard surfaces, 4lo is very bad to run on solid surfaces (best used for snow, mud, sand, gravel, etc)

You will notice a difference in power when running in 4wd mode, especially when you try to turn, you should probably avoid making tight turns on any hard surface

I have forgotten to turn mine off and easily done 70, I try to use it regardless of if I need it at least once in a while (anytime there is dirt, mud, sand, whatever) because if you don't use the 4wd system then the lubricants don't get circulated and problems can arise

 

[Vista Cruiser 69]

Hi Guys,
But this Auto 4WD feature - does it engage when ABS sensor spot wheelspin on rear wheel and then engeage the 4Hi mode, automatically? Technically no rocket science, all sensors are anyway on board. Unfortunately our winter here is quite mild these days so i tried to test the Auto Hi on grass with my 2001 Tahoe. Felt as if it did not work. I ruined the lawn but it did not switch to 4WD. It seems to require a couple of seconds to engage the gears, longer than my lawn was... it was about 3 seconds - which I think should be enough time
However, if that function is so slow then where is the point in it? It won't supply any extra security like on sudden icy conditions when rear wheels suddenly spin and you oversteer. So rather enaging 4Hi on my own at critical conditions instead of waiting for it. Who can tell how quick this auto system would normally engage the 4WD mode when sensing spin?

 

[lesterl]

2001 is a newer body style than the forum you are in Vista. When I had the newer body style the Auto sucked, like you said took a few seconds to engage, but that is normal AFAIK I suppose it is for lazy people who don't want to shift it manually...