wwest

Me too/also Robroy..UP!

Vehicles with manual transmissions have had "hill-start" (Hill-holding) capability for as long as I can remember.

No, I haven't, only read about, all over the internet, the problems owners are having when it engages and then disengages so abruptly as engine RPM rises to the level that the new lower efficiency torque converters provide enough coupling to overcome gravity.

"....smooth transition...." Hmmmm.....Ford has found a way, some way, to smoothly release the TC braking solenoid...?? Electronic brake application and/or release is anything but smooth. Note the feel of ABS, TC, or stability control braking application/release. If vehicle "roll" is not a requirement for arming Hill-Start then why doesn't it engage each and every time the brakes are applied while stopped.

"...does roll back..." Before stability control was included or after....?? Besides which a bit of "roll" is required to "arm" hill-start and then brake application "sets" hill-start.

http://www.autoguide.com/auto-news/2009/09...state-fair.html 4th paragraph. Then about 2/3's down the page.. Addition of Trailer Sway Control. ("to long-standing AdvanceTrac features".)

Ford seems to be hiding a lot of sins under the AdvanceTrac label/"cover". I wouldn't be too sure that "hill-start" isn't one of these absent being able to read a fairly definitive theory of operation of overall AdvanceTrac functionality. With the development and wider (beyond OD) use of a much more robust torque converter lockup clutch the need for a highly efficient, TIGHTLY coupling, torque converter has waned, seriously waned. So nowadays absent Hill-Assist most automatics would roll if stopped on an incline. Step on the brakes to stop the "roll" and hill assist engages automatically, holding the brakes on for you. That results in a slight DBW "enforced" throttle delay once you apply pressure to the gas pedal. Seattlelites are especially appreciative of this "feature".

Someone please correct me if I'm wrong. "The failing seal is the one for the inner side of the front halfshaft drive where is exits the PTO/PTU". "Grease" = 70 weight. "...so it's load cycle..." There is virtually NO resistance to the PTO's ring gear turning the pinion that drives the rear driveshaft UNLESS the rear drive clutch is engaged. Engage, SOLIDLY engage, the RDU clutch on a highly tractive surface and the result will ALWAYS be driveline windup and/or tire scrubbing. Since there is no sensor or sensor set that can be used to sense, predict, that the engine torque can/will too easily overcome the roadbed coefficient Ford has chosen to be pre-emptive in engaging, most of the time NEEDLESSLY, the rear drive. "...heat in the rear RDU.." RDU clutch as the "weakest link" would be the result of SLIPPAGE, purely. If the RDU clutch does not slip then the additional stress will show up elsewhere, say driveline windup and/or tire scrubbing are the most common. Driveline windup would obviously result in higher frictional losses in the PTO gearset teeth, along with many other points.

"Hill-Start" is a feature which will apply the brakes while stopped on a grade to make it easier for the driver to initially start moving uphill. "Hill-Assist" is a feature which automatically uses the brakes to keep downhill forward motion to a minimum.

It sounds as if you're describing the new Hill-Start "feature" being incorporated into many new vehicles. The control system detects that the vehicle "wants" to roll forward or backward and automatically engages the brakes lightly. Now that you want to go forward it takes a "moment" to disengage this feature. With the advent, and wide use, of STRONG torque converter lockup clutches the need for engine idle, or low RPM torque converter coupling coefficient has been significantly reduced. That has resulted in less "natural" hill-holding ability, thereby the need for this new "feature". Some vehicles only activate the hill-start feature if an unusual level of braking is applied.

Yes, I agree, intermittent braking, braking only after the downhill speed has "risen" will result in higher heat spikes than more even, constant, braking. That's NOT to say an experienced off-road driver wouldn't be just as good at modulating/moderating the braking as would the Hill-holding, Hill descent mode.

I suspect neither one of us can prove our point/position so I'll drop it here.

"hill descent mode" simply uses, and OVERHEATS, the brakes automatically rather of one's own foot power. No "true" off-roader worth their salt would be interested in anything less that a 4WD/4X4 with a transfer case. No even remotely involved in the sport but IMMHO the 4runner would be the minimum "fit". The Ford Flex...off-road....??!!

Broach: http://74.125.95.132/search?q=cache:5BWqC9...=clnk&gl=us "..engine oil and coolant..." Both of those have lots of extra room for expansion due to heat, whereas the PTO is virtually hermetically sealed. "..get over 160 degrees.." "...shuts down at 145.." Many posters seem to think the thermistor has been eliminated, seemingly at the same time as the manual control switch. Besides which the thermistor was in the rear diff'l case, was it not...?? And I rather doubt that Ford will market the new unibody Explorer as off-road ready/worthy, especially if equipped only with the Venza type F/awd like in the Escape, etc. Plus that is not where the majority of the market lies, most buyers are simply looking for additional wintertime on-road stability and traction. And doesn't a TRUE off-roader expect/demand a granny grunt low gear range that would require a transfer case implementation.??

I really, REALLY hate to refer to the racing venue, but... Have you ever asked yourself why all the racing "stock" cars that come from the factory as FWD only arrive at the track as RWD...??

The way I "read" the posts it is the passenger side PTO halfshaft seal that is being "broached". The driveline to the passenger side front wheel goes through the PTO and therefore it is the PTO lube that "broaches", leaks from, the seal. Am I wrong..?? When did Ford first know they had an overheating problem with this F/awd system...2007..?? Now, finally, a fix...2011. I'm anxiously/hopefully looking forward to the Sport Trac version of the 2010 unibody Explorer.....

"..slide in the direction you are going.." I was "going" north but the roadbed went west...... And it occurs to me(***1) that with FWD or F/awd you might not know just had slippery the roadbed happens to be UNTIL you begin a turn. ***1 '01 F/awd RX300 but rear tire chains get installed the INSTANT I feel they might be needed. Otherwise it runs on nice and quiet comfortably riding Bridgestone Turanza "summer" tires throughout the year. Actually the number for FWD is more like 100% since the only thing that can be done is hang on and pray(***2). Well, maybe a bit less that 100% as a relative few would likely know to quickly shift the automatic transaxle into neutral (as recommended by the AAA) and a few of those might even be astute enough to lightly, judiciously, apply the e-brake. ***2 The exception being FWD and/or F/awd vehicles with stability control wherein the rear brakes would be automatically applied the instant understearing is detected. RWD stability control will do the same thing but RWD isn't nearly as subject to understearing as FWD. AND.... 20% may even be right for RWD. But at least there is a recovery procedure, stear into the skid, for that 20% to react with.

"..slide in the direction you are going.." But I was "going" north but the roadbed went west...... Actually the number for FWD is more like 100% since the only thing that can be done is hang on and pray(***1). Well, maybe a bit less that 100% as a relative few would likely know to quickly shift the automatic transaxle into neutral (as recommended by the AAA) and a few of those might even be astute enough to lightly, judiciously, apply the e-brake. ***1 The exception being FWD vehicles with stability control wherein the rear brakes would be automatically applied the instant understearing is detected. RWD stability control will do the same thing but RWD isn't nearly as subject to understearing as FWD. AND.... 20% may even be right for RWD. But at least there is a recovery procedure, stear into the skid, for that 20% to react with.

Other than the seals having already been blown, compromised, there is always a "breather" method somewhere/somehow in any automotive gear box.

When, what model year, did Ford start using engine coolant for cooling for the PTO..?? Or are they only using it for the TwinForce engines due to the extra driveline stress...?? "..purely mechanical tolerances..." Yes, PTO ring and pinion, lube, and case HEAT-UP, mechanical tolerances change beyond design expectations....

A person doesn't always know when the surface traction coefficient is below the required level for acceleration AND lateral/turning forces. Otherwise things like TC and/or VSC wouldn't be required.

No, there is NOTHING that senses the level of torque. The system PRE-EMPTIVELY apportions engine torque to the rear when accelerating from a stop or from a low speed on the presumption, correct presumption, that that is the circumstance wherein front wheel traction would otherwise most likely, potentially, be lost. Otherwise the only time the rear drive is engaged is AFTER front wheelspin/slip is detected. Seems somewhat needless to me because according to the literature it is at that same point that TC activates, dethrottling the engine and moderately braking the front wheels in order to sustain engine torque at a reasonably high level. It would seem better to me to just simply engage the rear drive first on the chance that alone would alleviate the front wheelspin/slip. But then this is a rather DANGEROUS FWD at that point so I guess all available meaures to QUICKLY alleviate the danger might be appropriate. "...this does not make any sense.." Actually it does. It is during the winter months that the rear drive is likely be be "used" more often. It also may well be that the OAT sensor signal is used to dictate how high the rear drive coupling is commanded. Given this evolutionary design history, and FAILURE history, of this F/awd system I would not find it surprising that the "standard" (non-wheelslip/spin) rear drive coupling coefficient is llower in the summertime than in the winter. Note that the canadian owners seem to dominate the failure "column". Maybe different firmware north of the border, more "robust" F/awd operation..??

When in F/awd mode ALL driveline, drivetrain, components are under an unusual level of mechanical stress. This is especailly true for thse new F/awd Ford systems that automatically engage the rear drive with acceleration even on highly TRACTIVE surfaces.Therefore I would not find it out of the ordinary for the PTU to be overheating to the level that the lubricant is close to boiling and therefore "blowing out" the seals. Someone might want to try disabling (remove a fuse..??) the rear drive coupling clutch after a new seal is installed to see if that extends the seal life. Were I one of the Ford engineers I would seriously consider revising the system such that the rear drive only engages automatically (other than actual wheelspin/slip) when its raining or if the OAT is below 35F. It seems rather stupid to me to force the system endure the driveline windup and/or tire scrubbing when operating on a highly tractive surface.

Just EXACTLY what we should expect from a Ford Edge.... FANATIC....!!

Speaking of instances wherein the PTO was replaced, not just the seal. Anyone have an answer, looked at the TSB calling for PTO replacement.