You are feeling the center multi-plate clutch engage, transferring torque from the rear wheels to the front wheels. The system needs the whole four-wheel drive system to be engaged to work, so there is no mechanical shifting. The only component moving is the center multi-plate clutch as the individual clutch plates are charged and close-up.

You have an older first generation Expedition with the first application of BorgWarner’s full-time ControlTrac system in a full-size SUV. BorgWarner has obviously refined the system since then.

Newer second generation Expeditions, have vastly upgraded control hardware & software by BorgWarner to reduce the awareness of torque transfer. Third generation Expedition 4x4s are even more secret about torque transfer.



No, if the Expedition had a planetary or bevel geared center differential, it would supply torque to all four wheels, all the time while allowing for slipping between the front & rear drive shafts.

The Expedition’s center multi-plate clutch supplies torque to all four wheels, when needed while allowing for slipping between the front & rear drive shafts.

Full-time means the system can operate even on dry pavement, not whether the engine’s torque is going to all four wheels at any given moment. ControlTrac can operate (supply torque to all four wheels) on pavement, therefore its full-time.

 

Full time 4wd systems employ a center differential. The BW TOD transfer case does not have a center differential

The BW TOD system is a standard part time transfer case with an electronically controlled clutch engagement of the front propshaft.

If you chose to alter the intended definition to fit a new product, I guess that is up to you. There is a distinct difference between the two and as such should be considered with sperate designations. Typically they are, one is full time 4wd, the other is automatic 4wd, the BW TOD/Expedition is the latter.

I suppose you also believe that Mobil 1 is still a fully synthetic oil? They changed the definition to fit the product in that case as well. I prefer to stay with the orgininal definition in both instances.

 

No it's not the same thing. When in A4WD the mechanical components for supplying power to the front driveshaft are engaged, but the electric clutch creates a break, preventing the power from reaching the front axle. When the rear wheels slip the A4WD system powers the electric clutch allowing power to transfer to the front axle. In contrast, if there were no electric clutch for the front driveshaft, then automatic 4WD could only be accomplished by jambing the mechanic into engagement to provide power to the front axle. This is what GlassLeather&Wood meant when he said, "The 4x4 system does not shift into and out of four-wheel drive, as most misinformed people will tell you. Literally shifting from 2-wheel to 4-wheel drive is pure nonsense."

 

BorgWarner defines the 4x4 system as a automatic part-time/full-time system.

Below is article for you read concerning the direct development of the automatic part-time/full-time ControlTrac four-wheel drive system from BorgWarner’s testimony.

4-wheel drive steps back to the future - 1995-01-23 00:00:00 | Design News

You can’t argue with the people who designed the system (well, you can, but its pointless as they know more about the system than you or I). A 4x4 system does not need a center differential to be "full-time", it just needs something to take the place of the center differential and perform its job.

Its okay if you don’t fully understand how ControlTrac works, its somewhat complicated. Yet it is more cost effective to operate than a 4x4 system with a center differential. Electronically-controlled full-time four-wheel drive systems with center multi-plate clutch "differentials" are a marvel of modern technology.

 

From what has recently been said it seems that the A4WD systen has something like a posi unit in it that is operated electronically. Sort of applies a varied amount of pressure to the clutch pack depending on the amount of traction lost or needed at the front axle.
I think one of the first systems was similar in Jeeps a long time ago using a posi system only.

 

What makes you think I do not understand?

I think there are flaws in the clutch pack/electronic systems. An open differential with a manual lock is a much better system on and off road.

They clearly work differently than traditional systems, yet you want to confer a non-traditional designation. BW does it as a sales and marketing tool, because they KNOW a true full time system is the holy grail.

This is exactly the same situation where Castrol and Mobil had a suit over the definition of a "full synthetic" oil. Did you know that they may now legally claim "full synthetic" for oils that use blends of refined dino stock for a base?

So now we have *******ized definitions of full time 4wd and synthetic oil. That is something to be proud of.

 

Hey Greenie was *******ized supposed to be *******ized? That's not a bad word anymore as *******s are quite common now days. There are even a few that are our elected representitives. Lucky us.

 

Well I guess the post police don't consider it politically correct, yet.

 

Post *****!

Interesting what you can and can not say...

But I bet it lets poop get through, thats ****ty.

 

Okay you got me on this one, what letters are missing from *******ized?

 

Probably the B, the A, the S, the T, the A, the R, and the D. Usually the product of unplanned actions enjoyed by most of us wich results in single parenthood, Maury Povich and DNA testing with many strange results including a lot of yelling,screaming and laughter from the audience.

 

well i hate to bring up a old post, and one that went off topic..sorta

anyhow just found out today i'm having the same issue. flashing A4WD light and no front tire engagement. 4x4 high and 4x4 low work great. now i know A4WD worked up till a month or so ago. went to use it yesterday and got nothing but a flashing light.

which sensors do i need...i really like the A4WD setting in the fall/spring when the snow/ice is not totally covering the parking lots..ect otherwise its locked in 4x4 high all winter.

 

Read post #26, again, for a pretty good explaination of how our A4WD system works and then check your sensors in the T/case. If you have an early T/case the info may be different.
It seems that the sensors might get coated with debris from the chains and gears causing them malfunction.
Now that Greenie is gone we might stay on topic.

 

No kidding!! I have the same problem on my 97. Last fall when I was asking about it, I was having a hard time finding the right part from the parts store. They wanted me to take it out an bring it in to make sure. I wanted the new part so I could see what I was looking for on the T-Case.... Probably should do it this year before the snow flies again.

If anyone has a picture of the two sensors needed, that would make life a lot easier. Maybe part numbers from Advanced Auto, Autozone, Napa, Oriley, whoever.

Thanks!
Denny

 

pics would be a god send!

i meant to crawl under the expy this weekend but never got around to it.