2007 FEH AWD 26,000 miles. Started with a slight binding feeling in drive at 0-5 mph. Rapidly progressed to a speed dependent rattle, especially when coasting. I can't find a report of any one else having one go bad. No oil leaks. I'm just wondering if I got a bad one from the factory. I do run Nokian studded hakkapellitas all around in the winter, but they are the correct size and make a world of difference. I've also never been shy about where I've taken it, but I've always driven speed appropriate for the terrain. Getting 30-32 mpg roundtrip and getting a few miles back in the sticks at the same time has been a thing of beauty. Any ideas , feedback?
Thanks,
Pete

PS -sorry about the crosspost -I put it in the wrong forum at first

 

PTU..as in Power Takeoff Unit...??

That would be the STRESS point if the rear driveline is engaged improperly or to often in the wrong circumstance, or even if F/R wheel were to differ significantly for a distance, chains only on the front, say.

I would check and make sure the 12 volt PWM supply to the rear driveline clutch is being properly modulated and the PTU coolant flow is not blocked somehow.

"..getting a few miles back in the sticks..."

With 4WD manually engaged/over-ridden...??

The early versions of this F/awd system were prone to overheating, so much so that Ford has a warning indication of same and an advisory that the driver should pull over and allow the rear driveline time to cool down. Once the engine coolant was used to provide PTU cooling that indication was dropped.

Along with the cooling addition they may have reprogrammed the F/awd control firmware to make the rear driveline engagement not quite so aggressive and a manual over-ride would bypass that protective measure.

The Escape F/awd system was not meant to be used as would an actual 4WD/4X4 system, not as rugged/robust.

 

Yes- Power Take off unit. Luckily it's still well inside of the warranty coverage-it can't be cheap. My off road adventures are probably no harder on the vehicle than the average in-town drivers habits. . Its mainly been a function of having decent enough ground clearance. I don't drive it through water or in much mud. Mostly either dry desert or some mountain roads. Kind of steep but always very slow. I realize that this isn't a unimog or a landcruiser. I don't think I've ever put too much stress on the driveline. I have had to rescue a couple of cars from the snow before. These were both towed just a matter of feet and I was quite careful and used a nylon tow strap to reduce shock. The AWD system has never locked me out or given me the warning indicator.

 

If you have EVER manually engaged the F/awd system off-road then I would advise NOT telling the dealer that. Most off-road "adventures" involve, mostly, highly tractive surfaces, so manual engagement of the system would put an unusual level of stress, likely above design specs, on the driveline.

IMMHO the manual F/awd mode should NOT be used except on a reasonably continuous low traction surface, snow, ice, etc. Not even an oil slicked wet roadbed applies IMMHO. Let the automatic system handle those.

Do you have the warning indicator..?? I thought it was dropped once the PTU was being cooled.

 

Is/was a '07 4WD/AWD switchable? The Intelligent 4WD/AWD 'on demand" isn't switchable as far as I know. The traction control is though!

EDIT:
You might want to call the traction control on/off switch AWD on/off because traction control makes a 4WD become AWD.

 

AWD/4WD system is completely automatic. Of course I don't give the dealer any more info than is needed. However, I really haven't done anything that's not addressed in the owners manual (except for pulling a car or two of a snow bank). I guess I can just chalk it up to getting a factory defect.
Thanks,
Pete

 

Hmmm..

Hadn't thought about that. Since it is an operational aspect of TC that often causes the rear driveline to be engaged does turning TC off mean the rear clutch will not be engaged...??

I suspect not. It seems to me that turning off TC should only result in the front brakes not being used to enforce torque distribution to the rear. No front TC braking, no engine dethrottling necessary.

Anyone know the actual workings, answer..??

 

Based on my other thread here, 4WD is enabled with TC off. TC would direct power to whatever wheels that have traction.

 

The way it works as I have been given to understand it is that the rear driveline is engaged under only two circumstances. First, when moderate to heavy acceleration is "called for", and then only in at lower roadspeeds.

Second, the other instance, is if front wheelspin/slip develops due to too much engine torque being applied, even with light throttle openings, for roadbed conditions. In which case the initial plan of action is to engage the rear driveline.

Remember that as much as 1/2 of the engine, HSD system, torque can be routed to the rear. If that doesn't work and wheelspin/slip persists then I have little doubt that TC braking and engine dethrottling would quickly follow. probably 200-300 milliseconds total timespan.

My guess is that like many other TC systems if it is disabled the rear driveline will still be engaged in the same way, manner, and you will be allowed to initentionally use wheelspin to get unstuck and/or initially up and going.

 

Try replacing the U-joints first. I have had u-joints go out on cars over the years and the first one kicked my butt in diagnosing it because of the very symptom you describe: worse when coasting and speed dependent.

There are two u-joints between the PTU and the rear axle.

Roger that the rear axle should not be engaged when on a dry hard surfaced road, but a failing element in the drive line just might kick in the AWD feature by increased resistance...

U-joints are maybe $15-45 each and are not difficult to replace yourself with certain tools. Worth a shot and cheaper than a PTU.

PS wwest's musings on TC, the rear clutch, and so on are off the mark, musings of a guy that doesn't even own an FEH nor have the manual.