The PTU is only under STRESS when/if the rear clutch is engaged at some level, up to 100%, 50/50 F/R torque distribution. In the FEH that happens automatically, PRE-EMPTIVELY, with no input from the driver.

If the clutch is "open" or mostly so, little or no engine torque is being conveyed to the rear axle so the PTO is "free-wheeling", under no "drive" stress/HEAT.

The FEH system will go into 100% lock under low speed HARD acceleration, in a tight low speed turn, or in a moderate but accelerating turn.....REGARDLESS OF ROADBED CONDITIONS, HIGHLY TRACTIVE OR NO...!!!

Obviously during those periods, however brief, the driveline will be, might be, under SEVERE STRESS......HEAT...!!

In a true 4WD/4X4, excluding off-road use, owners are cautioned to NEVER have/leave the center "lock" engaged except on KNOWN adverse, SLIPPERY, roadbed conditions, and not to leave the system engaged once up and going regardless of roadbed conditions.

My guess is that the PTO becomes, by default, the weak link, since it also serves as a ~3:1 gear reduction/torque multiplier.

 

Ah yes, I have a much better understanding, thank you.

Gonna research the amp draw of the rear clutch disengagement mechanism (to determine if I need a relay or not), then determine any potential adverse side effects of electrically disengaging it. I have seen the post about pulling the fuse, but the switch idea makes more sense to me, it if is a viable option.

 

The FEH F/awd system uses a PWM, Pulse-Width-Modulated, duty-cycle electrical signal to control the rear clutch in a somewhat "linear" fashon. Possibly making it difficult to determine the required highest level current flow. So I would select a switch or relay based on the fuse value.

But please remember that when the F/awd ECU "thinks" it has "locked" the clutch the functionality of the TC and/or stability control might still be compromised. On the other hand it would be expected that simultaneously with the need to activate a "braking" functionality of this class, like actual brake application, the rear clutch signal will be INSTANTLY disabled.

 

I seem to recall that disengaging the 4WD causes a fault light on the dash as well.

Personally, I think it is foolish to mess around with any electrical component in an FEH; the CPU is programmed pretty extensively and specifically for the FORD gas/electric design.

Unlike some people who insist on intruding into a forum, I actually own an FEH...

 

Either a switch or pulling the fuse will cause your "wrench" icon to come ON and stay ON hiding/masking any other possible problems.

A trickier and harder soloution would be to fool the system into thinking the circuit is still there by "maybe" adding a resistor across the two wires going back to the rearend unit.

 

Personally, I think it is foolish to mess around with any electrical component in an FEH; the CPU is programmed pretty extensively and specifically for the FORD gas/electric design.

+1

Someone continues to post incorrect information about your 2006 FEH and we will leave it at that.

 

There are some aspects of the FEH that aren't unique to it, one being the 4WD system. I don't own a FEH, only a FE.

It was my curiosity of the 4WD system that lead me to this forum. Because of the thread I started here after viewing SG-II pictures posted by Billyk in another, Desert Dog/CarlD changed his original coding for the SG-II showing the correct rear wheel torque.

I myself at first believed it was a On Demand only system which it clearly isn't!

 

Yes, even Lexus, for the 2010 RX350, adopted the same F/awd system as used in the FEH. First used by Toyota in the Venza. Even the Porsche Cayenne now uses this same system, but for R/awd, and quite obviously an entirely different firmware suite.

 

It really is an "on demand" system (well, sorta), automatic F/awd system. The thing is, the factory engineers have pre-determined, based on various conditions, when "demand" might be appropriate and programmed the rear clutch control firmware accordingly.

It could be "wired" to be fully engage constantly on a known slippery surface but then the burden would be on the driver to be extremely diligent in disabling it when otherwise it would become seriously overstressed.

 

It engages every time one leaves from a dead stop no matter what the road conditions are so it can't be called a On Demand System.