4 Wheel Drive all of the Time?

I was just reading the latest issue of Consumer Reports and there is a review of the new Chevrolet Tahoe.

In the article it says, “The four-wheel-drive system can stay engaged at all times, which is a plus.”

I don’t understand.

Can someone explain what that means?

How can you drive a vehicle with 4WD always engaged?

Does the artical mention anything about “Autotrac”?

I have Autotrac on my 2000 Blazer. In Auto 4wd the transfer case is sends power to the front axle differential, but the hubs are not engaged. If the 4wd system detects slippage in the rear wheels, it then engages the front hubs. In this mode the Blazer can be driven on dry roads with no damage (other than mpg). It’s useful the snow and heavy rain and works fairly transparently.

Ed B.

The article does not refer to “Autotrac”. There is no further explanation.

Usually, CR explains things much more clearly. If “Autotrac” was what they were referring to, I would expect them to have mentioned the effect it would have on mpg.

The Tahoe must have ‘full-time’ 4wd, which can be left on all the time. To be ‘full time’ it has a center differential, which ‘part time’ 4wd systems lack.

From the Tahoe web site, it looks like all 4wd Tahoes have Autotrac, so no reason for CR to mention it.

Our 2003 Toyota 4Runner V6 has full time 4 wheel drive that may be engaged all the time. The 2003 Toyota 4Runner V8 had permanent 4 wheel drive. This model always ran in 4 wheel drive and the 4 wheel drive could not be disengaged. We only use 4 wheel drive when we need it, but the owner’s manual says it can be left engaged all the time but with a slight penalty in gasoline mileage. As another post said, there is a center differential.

Got it.

Thanks to all who explained it.