2007+ Expedition & Navigator2007, 2008, 2009 and 2010 Ford Expedition and Lincoln Navigator
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Can someone explain to me (in a more technical sense) how the 4 auto feature works, mechanically? Is it a geroter based system, or electric, or...???
The info says it "transfers torque where needed"... does that mean it runs the front end always in addition to the rear end, or can it run the front end to the exclusion of powering the rear like some AWD set-ups?
I understand how the Jeep transfer cases work with the all-time feature in the Selec-Trac and the geroter set up in the Quadra-Drive... I'm just not familiar with exactly how the auto feature words in the Ford. I know it engages much more quickly than the Quadra-Drive (geroter) in my old Grand Cherokee.
Based on my experience driving Fords with 4x4 Auto the front drive train is always connected with the switch in that setting and any power transfer is activated electronically by engaging a clutch. In 2WD the front drive line is disconnected.
I leave the switch in 2WD unless I think I'll need 4x4. I can feel the drag of the front drive line when I switch to 4x4 Auto at moderate speeds.
I know the Ford system is pretty advanced. Don't know how, but it has the ability to send all the power to one wheel front included if need be, but if it is doing that there is ahigh likelihood that it is braking 2 or 3 of the other wheels. So yes, it can send 100% to the front, not just 50/50. Don't know how the hell it does it though.
Interesting note is that my 03 Fx4 came standard with a limited slip, but since I ordered advancetrac it deleted the limited slip option. I've really loved the operation of the system. I have an 08 ordered.
The 4-auto can send all the torque to one wheel by using the braking system to stop the torque to one, two or three wheels.
If the computer sense one wheel is spinning faster than the others then it will apply brakes to that wheel in an attempt to send the torque to the other wheel (ala open diff). If you are in the predicament where three wheels are levered off the ground, supposedly all the torque (or a lot of it) can be sent to that one wheel by braking the others.
Sounds good on paper and probably works on the street for the most part. You won't see it in any real off-road capable vehicles though.
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