Waldo

So wwest, by implication you're trying to say that rubber properties are not affected by temperature. Do you really believe that? Have you ever watched a motor race and seen what happens when a car comes out of the pits and tries to go fast on cold tires? As I posted earlier, I've witnessed, with my own eyes, cars with winter tires on dry pavement driving faster around an autocross course than cars on real summer autocross tires in cold temperatures.

Well this is obviously true, as the attack was started by you against wwest for this very reason. He merely offered a theory, you immediately jumped on him saying he was WRONG. I merely pointed out how you were wrong to dismiss his theory, it is possible, but very unlikely. Unlikely and wrong are very different things. You then tried to compare an over-retracting piston to a frozen piston, which clearly shows your ignorance of brake systems as they are completely opposite issues.

Now, now, it's usually easy to pick on wwest, but in this case it's you who's WRONG. A warped rotor can cause the piston to retract more. Every time the warp hits the pad, it pushes the piston back into the caliper. And yes one brake piston retracting more would cause exactly the symptoms the OP describes. All the brake fluid must push that one piston up to the pad first, then it can start to actually apply the brakes at all four corners. To the driver that would feel exactly like a loose pedal and depending on how far the piston has retracted, it could go to the floor. Last time I changed the pads on my Focus (you retract the pistons when you change pads), I forgot to pump the brakes and started rolling the car down my driveway (towards my wife's car). I nearly had a heart attack as the pedal went right to the floor, but some frantic pumping brought the pistons back up to the pads and stopped the car in time. A frozen piston is a totally different scenario. A frozen piston doesn't move at all, so the brake fluid can't push it and thus immediately starts acting on the other three calipers. In fact a frozen piston would make the pedal feel tighter and shorter, if anything. But, it would take a LOT of rotor warp to cause as much issue as the OP describes. Thus I think this explanation is highly unlikely to be the cause. It's far more likely to be a leak that's allowing air into the system but not a lot of fluid out. Even though the master cylinder has been changed, I'd check it again, especially with regards to it's interaction with the booster, as in DJ Nap's case.

Because tread wear ratings are meaningless numbers created for marketing hype. Plus winter tires have much deeper tread than summer tires.

I was agreeing with you right up to there. As Allen pointed out, the tread compound of a tire is designed to work in a specific temperature range. Get it outside of that range and the tire will not perform as it's designed. I've actually been to an autocross in December where some guys running on snow tires were running faster times than guys running on racing slicks. And the course was 100% dry and clear, but the temperature was right around freezing.

Nope, no Ford that I know of has ever used the radio display for any temperature readings (not including navigation systems). The manual climate system doesn't have an external temperature sensor, so you won't have an external temperature reading.

You mean like the Ford Explorer??

This is not true. The Ford AWD system will send a small amount of torque to the rear wheels at ALL times. It is usually as low as about 5% during most highway-type driving, but it's always more than 0. Otherwise the clutches would get cold and when you did want to engage it in your two conditions, it would be abrupt.

You can do anything you want to the electronics, but the reason the AWD gets worse fuel economy is because it is heavier and because of additional friction from the additional driveshafts. So to truely get the fuel economy of a FWD, you need to remove the rear halfshafts, rear RDU, driveshaft and change the transmission. Clearly not a cost-effective solution.

I know this probably isn't the right thread, but: 1. That's opinion, I consider it a clever engineering solution for a lower cost product 2. Not true, the warranty data on real chrome is much higher than the chrome-clad 3. I don't think you can re-polish real chrome either, if it's a big scratch, just replace the plastic, that's cheaper than having a wheel re-chromed 4. Fixing a bent wheel is exactly the same whether it's real chrome or chrome-clad. You just put on a new plastic cover if it's broken. 5. As akirby pointed out it's a manufacturing defect. Clicking noises are common on removable hubcaps, but that's a different style of design. Of course there is, the cost difference between a real chrome wheel and a chrome-clad wheel is HUGE! (The real chrome wheel starts out as an alum alloy too). It's on the order of hundreds of dollars per car, not just pennies. Would you pay $200 more for real chrome vs chrome clad? I know I wouldn't. As for the leather, it's the same thing. It may not be real leather, but the vinyl on the seat backs of my 2002 Focus feels and looks better now than the real leather on the bolsters. I would actually prefer if it was all vinyl instead of leather. It's like synthetic oil vs conventional oil. Sometimes the imitation can actually be better than the original.

That's a pretty long rant without actually mentioning anything wrong with the plastic covers. They may be "immitations", but chrome wheels only exist for appearance, do you really think they don't look as good? Clearly the appearance was good enough to fool you on the test drive.

Just press 3 and 6 together and it will go to the diagnostics screen. But you won't be able to change configurations in there, just run tests.

First of all the PTU is connected to the engine 100% of the time, so it's load cycle is very different than the clutched rear end. I suspect it's actually the action of locking and unlocking the clutch, not the actual load transfer that creates the heat in the RDU anyway. Besides if Ford new about the temperatures in the RDU and put in a thermister, why wouldn't they do the same in the PTU? But the real flaw in your theory is that even if the PTU grease was overheating, it doesn't touch the seal that's failing.

I've got a direct email from a Ford transmission engineer, what do you have? I also spent 10 minutes reading the 2010 Edge service manual and determined most of what you're saying isn't possible and the very detailed (including a specifically made video) repair instructions don't seem to line-up with your theories. And about the hill descent control, are you saying that my parking brake is going to overheat if I park on a steep hill? As Edgenut points out, the slower you go, the less heat you generate - you disspate the potential energy of the vehicle over a longer period of time.

I didn't know "broach" could refer to piercing, so if that's the case then no, the issue is not broaching. The seal is not getting pierced, it's getting compressed. A PTU is not hermetically sealed, there is a breather vent and besides, it's not full. There's still plenty of air in there as the fill level is only about 2/3rds of the way up. Besides, the vast majority of the leaks are actually transmission fluid leaking out, not the PTU grease. That's the same transmission fluid that passes through the transmission cooler by the way. The new Explorer will feature a specific off-road and hill descent mode, marketing specifically towards off roading. It also has higher ground clearance and beefed up suspension to meet Ford's off-road standards. If you want a non-off-road 7 passenger vehicle, Ford already has the Flex.

I assume you mean "breach", not "broach". Yes the seal is leaking, but the cause is sideload, not temperature. The driveshaft is pushing down (or up, or sideways) on the seal because the shaft is not located correctly. Over (a short) time, this extra load that the seal was not designed for causes it to fail. This is exactly like the failure of a "blown" shock, the seal is sideloaded and eventually fails, causing the fluid and gas to leak out. Think about it, even when overheated, PTU oil won't get over 160 degrees (the system shuts down at 145 I think). Engine oil and coolant will see temperatures far above that on a regular basis and you don't hear about seal failures on those parts. I still don't understand why you think there's a temperature "problem". Temperature is always a concern and is considered in the design of the system. Look underneath an Ecoboost Flex and you'll see a duct that blows fresh air right up to the PTU. The Explorer needs additional cooling because it's expected to have a more severe life including off-roading. PTU temperatures are a design challenge. But Ford has addressed the issue from the beginning, which has prevented it from being a problem.

Seriously, the racing tie-in is the best you can come up with?! Weight transfer under acceleration gives rear wheels more traction, which is great for PERFORMANCE. You can't compare PERFORMANCE with SAFETY. They are two totally different conditions. RWD helps to acceleratate out of a corner faster. It does not help recover from a skid, in fact it makes it harder. If you've ever watched any racing you will notice that there are plenty of examples of RWD cars understeering right off the track. Additionally the cars that are converted to RWD are also usually changing engines to one that wouldn't fit in a FWD configuration, never mind that a FWD drivetrain can't take 500+ HP. FWD does not cause understeer by itself, unless you are on the gas. If you are trying to save yourself from a crash, you should not be on the gas. FWD cars tend to have higher front weight distribution, which does contribute to understeer, but most AWD cars even this out, whether they are FWD or RWD biased. And I'm not quite sure why you think all you can do in a FWD understeer situation is hang on and pray? There are plenty of options, the most obvious one being let off the gas and even touch the brakes, which again is what EVERYONE knows how to do. A more astute driver will also recognize that the tire slip angles are oversaturated, and will actually reduce the steering wheel angle to get a little more front grip, a trick that works equally in FWD and RWD cars.

Of course not, but a RWD driver doesn't know this either. When you are surprised by an unexpected slippery surface, would you rather the front wheels lose grip and you slide in the direction you are going, or the rear wheels lose grip and you spin around backwards? I'd wager that 90% of drivers can deal with the first situation and only 20% of drivers can deal with the second.

The next Explorer, 2011. As I posted, the issue is in the tolerance of the bearing that holds the linkshaft, the one that hangs off the engine about a foot away from the PTU. Not really related to the heat in the PTU at all.

Then let off the gas... Why are you trying to accelerate in a turn on a slippery surface anyway?

Ford's just as smart as Mazda, they are doing exactly what you describe on the Ecoboost versions which use exactly the same hardware. In fact I even beleive they will use a water-cooled PTU on the new Explorer. But the problem with the leaking seals is not due to temperature, it's purely mechanical tolerances.

The PTU lubrication is cooked after it leaves the PTU and lands on the exhaust. The exhaust is much hotter than the internals of the PTU. This has been well documented. I'm not quite sure how else you could smell it.

I really don't understand this. When you lose traction in the front of any vehicle, you continue to go straight. The only thing a driver needs to do is lift the gas and/or apply the brakes, which is what anyone's natrual tendency would be to do. Having driven FWD vehicles in winter conditions for 16 years, I can't say I've ever had a DIRE condition. The only incident I ever had was when driving my parent's RWD Aerostar. Heck I've even used FWD wheelspin to spray snow onto the sidewalk and pedestrians as I drive past...

I guess book learning doesn't teach you much about manufacturing. When you build hundreds of thousands of parts at relatively quick line speeds, you end up with a lot of tolerance variation. If you end up with a couple of parts on opposite ends of their tolerance ranges, you end up with problems like leaks. From what I understand (from real sources, not books), the issue with the Ford PTU is a tolerance stack-up between the halfshafts, the seals and the bearings the link shafts mount to that essentially prevent the shaft from sitting straight in the seal. Ford is/has been working on eliminating these conditions, they have not made any changes to the software strategy. It has nothing to do with temperature.

Uhh, there's a little more engineering going on here than you obviously understand. F/AWD systems are optimized for what they are. The rear RDU and halfshafts are not sized for the full torque of the engine nor is the heat dissipation of the system designed for significant RWD use. Doing what you suggest will cook and break the system rather quickly.