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Questions About The 4x4 Driveline...

ehahn

Charter Member
Full Member
Joined
Feb 6, 2002
Messages
80
Hi all,

The answer to these don't seem to be included in either the owner's manual or the specs on the Chevy site.

Q1: When operating in 2-Hi mode, is the front axle disconnected at the transfer case, or just at the hubs?

Q2: What is the front differential? Is it open, a simple ratchet, or a welded spool?

Q3: Any prohibitions about using 4-Hi or 4-Lo on pavement on occasion?

The reason I ask is that I was backing a trailer into a tight parking spot at the top of a grade. Because the spot itself was off pavement, I engaged 4-Hi (which helped when the rear wheels left the pavement).

After disconnecting the trailer, I pulled forward down hill and to the left, and forgot that I had 4-Hi engaged. I made a fairly sharp turn left, and it felt like the front was binding - I even got a bit of tire chirp. I immediately remembered that I had 4-Hi engaged and switched it back to 2-Hi.

So...what is the front diff, and did I do a no-no by turning sharply on dry pavement?

ed
 
At the risk of showing my ignorance, I believe that 2HI is disconected fromn the transfer case - AutoTrac connects, but doesn't engage until slippage occurs.

4 HI forces engagement and does seem to make turning a real bear - can't say that it makes sense, but have tried it. My AWD Jeep never had this much trouble or bindint.

For what it is worth, I know of someone who launches in 4 HI at the dragstrip - gets good starts too.

 
Here's my understanding . . .

When in 2-Hi, both the front hubs and transfer case are unlocked.

When in Auto mode, the hubs are locked and the transfer case unlocked unless slippage is detected - then the transfer case locks up.

In 4-Hi, obviously, both the transfer case and hubs are locked.

The front diff is a simple open unit - the binding comes because there is no diff, or viscous coupling or anything in the transfer case - it's a solid connection. Hence in turns on dry pavement, there's nothing to give. Don't think binding it up occasionally is the end of the world, but is to be avoided.

 
If during 2-Hi the hubs and transfer case are unlocked, then why does the 4WD model get less gas mileage then the 2WD model? Is it solely because it is dragging around almost 300 more pounds?
 
By the way, I was tetering on the 2WD/4WD fence as to which to buy. The AutoTrac system sold me on the 4WD model. I think even my wife can benefit from this system and will use it during bad weather.
 
midlife:

Yup - it's the weight and a tad more wind resistance as it stands 3/10 of an inch higher...
 
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