Regarding the info on overheating: this can be measured by measuring the resistance of the solenoid. Since the solenoid contains a large amount of wiring, the resistance of that wiring can be used to infer temperature.

 

The above is just plain and simple an un-necessary slap in the face.

"..if you understood engineering..."

A "good", understanding, engineer would write posts that are understandable to the general public, certainly so when it is expected that the primary audience consists of John Q public as is the case "here".

 

Yes, provided the solenoid wire has enough of a positive or negative resistance temperature coefficient. I doubt that the copper wire of the solenoid has enough.

I still suspect. strongly suspect, that Ford simply backed off the firmware control of rear drive functionality. Additionally if the dual clutch was so highly subject to overheating due to "planned" slippage, and the response were to be to fully lock the dual clutch as has been stated, that would simply move the stress component to other aspects of the driveline.

Putting the PTO at risk for early failure.

Maybe why the other marque using this same F/awd technique began using engine coolant to cool the PTO if the dual clutch began to overheat and had to be locked.

Much, MUCH simpler to just "relax" the firmware control and tell the purchasers that the FE/FEH is NOT for off-road use.

Shame the CX-7 isn't available with the Prius hybrid system.

 

They might be monitoring the current, so if the resistance changes, so will the current. Not sure how they could do all that in between the operating pulses though!

Anothe interesting point is that Ford uses the term "solenoid". A solenoid is a coil when energized, usually moves a core to make a physical or mechanical movement. Like open/close a valve, shift a hydraulic spool in a transmission. Solenoids open/close valves on a furnace.

I've seen pictures of the unit that's supposed to be used in the 4WD FE/FEH. I've read about that company also where it says that their products are used in the Ford Escape among others. It shows a coil and several clutch plates, somewhat similiar to the electric clutch on a A/C compressor. I don't think that they refer to the A/C clutch as a solenoid!!!

 

Hmm, almost missed this gem of a post! Here I thought that you had come down off your high horse. No such luck! If your really a engineer, you should learn how to read technical information better, so what you quote isn't twisted or incorrect.

Leaving out that part suggests that you only get rear wheel torque when slippage is detected. That is not true!

 

This is a bit of a Subaru commercial, but I like the ramp system that was used to test the AWD systems of the various vehicles:
http://www.youtube.com/watch?v=ooQRxlChvMw

Any thoughts on how the FEH AWD would perform on the ramp tests? Would it be as good as the Subaru seems to be?

 

Yea really wana see the FEH on that ramp too! even if it don't make it, it be a good test of our system.

ooo and insert joke here about toyota not getting up the ramp.

 

Hmm, good video! The FE/FEH is a asymmetric 4WD but until '09 the FEH didn't have traction control but still neither would perform as good as the Subaru which has symmetric AWD.

 

Here's a video with an early model 4WD FEH doing some off road passes and definitely engaging the rear wheel drive. You could expect similar drive train behavior in cold climates.

http://www.youtube.com/watch?v=P1iHGwj7MUA

At 5:17 there's a big flex put on the suspension and you see alternate front and rear wheels spin at the same time. That is followed by a somewhat impressive hill climb.

I expect all 2005-2008 models would perform the same as in the video but I can't help but wonder if the 2009+ models would do better with assist from the AdvanceTrac programming/controls.

(Sorry, wwest, it doesn't look like they disabled the FWD)

 

All right guys, this thread is way off topic. Either continue in response to the original question (Cold climate), or start a new thread about 4WD and the FEH.