4WD System

[RyanZ71]

on my 99 Silverado Z-71 I have 3 buttons,

1. Auto 4WD

2. 4Hi

3. 4Lo

 

I'm not too familure with Auto 4WD, what is its purpose compared to 4Hi?

[burgundyz71]

In 4Hi of course your in 4WD and in Auto your truck's not in 4WD until there is rear wheel slippage.

[99silveradoz71]

If you've got light snow or slush, the auto works well...kicks on when it's slick to give you added traction. It's a good compromise so you don't have to jump 4hi to 2 all the time.

[Shaners]

In "Auto" the front differential is engaged but it is just free-wheeling until tire spin is detected at the rear. At that point the transfer case will automatically engage until traction is regained.

 

The system works well when you are in conditions where you don't need 4wd constantly.

 

For bad conditions like mud or heavy snow, then just use 4-hi or 4-lo and lock the T-case in permenantly.

[99GMCZ71]

When i use auto 4WD and make a turn, you can feel the front wheels grabbing some. Is this normal?

[Bish]

Yep...normal. In 4wd on dry pavement, front wheels are locked to rotate exactly the same. When turning, the outside wheel travels farther than the inside wheel. THis makes the wheels want to turn at different speeds, 4wd won't let that happen so what you feel is the tire slipping on the pavement. VERY BAD FOR YOUR DRIVETRAIN ON DRY ROADS!