driving in 4WD Auto

[toddious]

are there any downsides to driving in 4WD Auto all the time? i have a 1996 limited with air ride suspension, so putting it in 4WD Auto boosts the car up and inch or so, but i was wondering if it would hurt my gas mileage, or any other aspect of my car. thanks!

 

[matey]

besides useing a lot of gas its not good for the transmisson to be in 4x4 on bitumen surfaces if you only drive on sand or gravel it should be fine but unles you like replaceing transmissons i wouldnt do it

 

[Texplorer]

If you put it in 4wd auto its not recommended that you go over 55 I think. It could potencially hurt other parts of your drivetrain if you left it on. Your ARC also isnt meant to be on all the time so you might hurt your shocks also.

 

[toddious]

so even though it says "auto" it's still gonna be putting it in 4wd? i thought "auto" meant that it only put it into 4wd when the tired were slipping?

 

[Blee1099]

I believe Auto 4wd puts out 5% or something like that to the front wheels until you reach a certain speed around 30 MPH. Why would you want to keep your truck in auto 4wd? I believe the 96 have a 2wd function on their control trac, I suggest just keeping it on that while driving and when you get into some inclimate weather, throw it into auto 4wd.

 

[Bronco638]

toddious,

I don't want to sound like a smart a$$ but what does the owner's manual say? I'll be more than happy to have a look at mine if you no longer have access to yours.

Dave.

 

[checkedout]

"C-Trac Function

The new C-Trac transfer case (7A195) transmits torque to front wheels through an electromechanical ball ramp clutch after a predetermined delta speed between front and rear driveshafts (4602) is exceeded. These driveshaft speeds are monitored using Hall effect sensors that send signals to the new on-board Generic Electronic Module (GEM). Upon observing an exceeded delta speed, the GEM then activates the transfer case clutch coil with a varying current to minimize the delta speed.


Low Range Function

In low range, the transfer case's electromechanical clutch locks the front and rear driveshafts for maximum 4x4 traction. The transfer case motor also rotates a cam that moves a range fork to the four low position. This range shift is accomplished through a planetary gearset which changes the torque to the driveshafts from a 1:1 to a 2.48:1 ratio.


2WD Mode

In the two-wheel drive mode, the transfer case's shift fork is moved to the high position and the electromechanical clutch is turned off. One hundred percent of the torque is therefore sent to the rear wheels."


so it would appear that a minimal amount of torque is always applied to the front in 4auto which would increase wear and gas usage.

 

['96explorereddiebauer]

Our system is different from conventional 4 wheel drive. When it's in Auto mode, the Limited's suspension will rise an inch to give a little more clearance up to 58 mph, that's when the height will lower back to stock height. In Low, the height will go up 2 inches up to 38 mph. If the speed is greater than 38mph, the height will lower an inch to keep the stability of the vehicle.

But back to 4 wheel drive. It won't hurt anything in Auto mode. It won't be hard on the tranny b/c there aren't any power going to the front wheel unless something sensed that the rear wheels are slipping...that's when the front wheels get to do something. There's also no speed limits. Like I said, the front wheels won't get any action until one of the rear wheels slips so speed isn't an issue. Since we don't have 4x4 High mode, I'm not even worried about killing any hard parts down there unless I'm in Low.

 

[toddious]

eddiebauer thanks for the help (everyone else too!), but what you said is pretty much exactly what i understood about the drive shaft and transfer cases activities while in 4wd auto. what you said about 4wd low though, you said the suspension lowers again after 38mph's..... my owners manual said something about not driving in 4wd low over 15mph? is it really bad for the car? or is that just a precaution?

 

['96explorereddiebauer]

Oops...typo. It's 30 mph instead of 38 mph. It's better not to go over its recommended speed or damage may result, but that's what the shop manual said about its height adjustments. So...when the vehicle speed is below 30 mph, then the ride height will be 2" taller. If the vehicle speed is above 30 mph, then the ride height will lower to 1" instead of 2". Sorry.

 

[toddious]

thanks alot buddy

 

[Texplorer]

One quick qestion, If you are cornering sharply, like a U-turn, your outside wheel rotates considerably more than your inside tire, can that excess rotation be percieved as wheel spin therefore engaging the front driveshaft while in 4auto?

 

['96explorereddiebauer]

I do not think so. The only way that the front axle would be engaged is when one or both the rear tire is/are slipping. Read the description posted by checkedout about the Control Trac system.

From the description, I'm guessing the computer senses the differences in speed at the drive shaft instead of a single wheel so that's why the front axles won't engage unless you're flooring it as you're turning, causing some major slippage in the rear axles.

Haha...try it out. It's fun!!