wwest

To hear wwest talk, fwd is the most dangerous thing since the Corvair.

Actually now that you thought of it the Corvair was only "unsafe" in certain specific instances as is any FWD or F/awd vehicle.

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.

"..It has nothing to do with temperature..."

Having experienced, apparently along with many others, the horrid odor/smell of OVER-COOKED PTO lubrication I think I'll just stick with my theory. And I am NOT speaking of 70 weight lube leaking on hot exhaust components.

In other words, you have no source from Ford that says they had to detune the rear drive engagement.

So, you think that "beefed up", made the PTO more robust...??

Then why not go back to allowing the driver to "lock" the system in F/awd mode. Maybe even put the thermistor back in to warn the driver of impending overheating...??

Back when the electromechanical linear coupling clutch was subject to overheating what did Ford do to alleviate the problem so the thermistor could be eliminated. Take the manual lock ability away..??

Then the NEXT weakest link began to fail, the PTO....

Mazda apparently had, or foresaw, the need for cooling the PTO and did so. Just what do you think Ford did when the PTOs began to fail.. if not detune/derate at some level..??

And if Ford did detune/derate the F/awd functionality how would users EVER KNOW.

Oh, keep in mind that detuning/derating the F/awd functionality via new firmware "FLASH" is something that can be done in the field, by the dealer, without ANY customer knowledge, as the replacement PTO is being installed.

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.

Assuming only low, low, speed for off-road.

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...

"..lose traction...you continue to go straight...."

And if that wasn't what you were trying to do....?

ABS is there so you can maintain directional control during severe braking or any level of braking on a slippery surface.

TC is a comparable "nanny", but "inverse".

My PTU is leaking and will be replaced next week. First noticed smell then saw spot on floor.

Overheated, burnt or boiling 90 weight gear oil can smell pretty horrid, a lot like a leaking natural gas line IMMHO.

Your PTU is leaking because that is the weakest link in the F/awd "chain". With the rear drive engaged on dry pavement the entire drive train can/might/will be under SEVERE stress. Components overheat, the 90 weight in the PTO/PTU literally BOILS, expands ovecoming the seal, and eventually the pto fails.

Along with a new PTO you can expect a firmware revision to reduce the overall functionality of the F/awd system such that this doesn't repeat. In the alternative Ford may decide to use firmware modifications to simply detune/derate the engine, especially the V6, when starting off, "WOT" acceleration, from a stop or low speed.

Mazda (CX-7, Tribute) has added cooling, engine coolant circulation, to their PTO so that is doesn't overheat.

Source?

The readily available historical record, F/awd design evolutionary record, here and there on the internet.

Start here:

http://www.fordedgeforum.com/index.php?showtopic=1654

I never had a car roll back like this edge does even on slight inclines. I had 2 different re-flashes done and it did absolutely nothing. Was told by dealer the flash works on some and not on others. It really is hit or miss with these guys. I just learned to live with it and it doesn't really bother me now, but at first, I thought the car slipped into neautral on my first incline.

With the advent of good robust lockup clutches to bypass the "lossy" torque converter the converter stall speed has become less important, a lot less important. So what you are likely feeling is the effects of these new torque converter having a much lower torque coupling with the engine idling. Lower load on the engine when stopped, a very good thing for FE, as I'm sure you will appreciate.

Many modern vehicles now have a "hill-holding", "hill-startup" new TC brake control feature to make up for this new lack of torque converter "holding" capability.

The PTU sends power to the rear differential all the time. The rear differential determines when to engage the rear wheels, not the PTU.

 

You need new books.

"..The rear differential determines..."

No, in reality the electromechanical clutch housed within the rear differential case is used to control, linearly control, the rear drive apportionmant.

You miss the point. The ENTIRE drive train is put under additional stress when the rear drive clutch is engaged. In the past, apparently, the PTO/PTU has proved to be the weak point, weak link in the chain. Mazda, seemingly, approached the problem via additional cooling of the PTO. One must assume therefore that ford simply "derated' the f/awd capability via firmware modifications.

The owner's manual has quite a bit of cautionary verbage on off-roading. It pretty much states the Edge isn't built for off-roading and specifically states it is not and does not perform like a 4WD and should not be used for off-roading. I would bet they would want to deny any warranty repairs if they believed the damage was due to off-road driving. Some of the comments talk about the AWD system being prone to overheating and damage if you get into exessive wheel spin. I haven't had a chance to read up on the power distribution system but I would think it is fluid driven like an auto transmission instead of gear driven like an old fashioned transfer case and a lot of continued power transfer under rough conditions could be hard on it. I won't be climbing any mountains with my wife's Edge.

When Ford discovered that the numerous PTO/PTU failures were due to driver misuse (over-use..??) of the F/awd system they "retuned" the control firmware to make the system less useful. Less useful, less stress on the drive train, no PTO overheating, fewer failures. Mazda, CX-7, on the other hand, went to cooling, engine coolant flow, of the PTO as a solution.

Having a 16 year old and a 15 year old who go to a magnet school, my wife has to drive them to school every day. My 16 year old daughter is not quite ready to drive to school on her own, so my wife rides with them in the Explorer, then takes the Explorer to work. At 3:00, she leaves work and picks them up at school, and my daughter drives her back to work then drives home. Consequently, my wife has only driven her new Edge AWD a few times.

 

It is raining today and my truck was washed and waxed on Sunday, so she called me and told me to take the Edge to work today. Woohoo! That thing is a freaking blast to drive in the rain. Taking off at full throttle up a hill while turning and there was no wheel spin whatsoever. The glass BAMR really muffles the sound of raindrops. I thought this was a soccer mom car, but I may be wrong. What a fun drive, and all the while, my 2008 F250 is safe and dry in my garage. The only things that it needs are about 100 more horsepower, to be lowered about two inches, and better tires...then I could race it in SCCA races!

"...about 100 more horsepower.."

In that case the engine/transaxle ECU control firmware would be tuned to automatically detuned/derated during low speed WOT acceleration, ceratinly so entering a tight turn under hard acceleration.

It was once thought that the limit for FWD would be ~200HP. Then it was discovered/decided that if the engine were automatically detuned/derated as above the public could be sold, safely sold, HIGH HP/Torque engined cars. Cars such as the FWD Cadillac with NorthStar engines. Nowadays they just automatically move some of the engine torque to the rear wheels during low speed acceleration to help alleviate the hazards of FWD and F/awd vehicles. Add more HP and fall back to solution number ONE.

Looking for someone (drivetrain engineer) that can help with changing thresholds for the advancetrac/abs to limit overide in offroad conditions yet still manage torquesplit to help preserve the fragile cv's.anybody?anybody?

Assuming only low, low speed for off-road the simplest thing to do would be to add a switch to supply a constant 12 volts to the rear drive coupling. No need for disabling any "nannies" because if this modification doesn't "work" in a specific offroad situation you will want "their" help.

Personally, if I owned one of these new F/awd systems (never, NEVER!) I would disable the front drive and wire the rear drive as above for normal road-going use. Either drop a front halfshaft or use the manual coupling available at ramcotowing.com.

I have read that the Ford system can transfer a large amount of the torque to the grip wheels and that it is one of the better ones out there so far.

? How does this compare to the Jeep drives?

? Is there any real comparison as to how well it works in snow vs. other true 4X4 systems?

 

Edge/MKX is on my short list to replace our aging 2001 Grand Cherokee with SelecTrac... however one concern I have is that it will not be as capable of getting up our steep driveway in the winter months. While the Edge has more electronics and sophistication, I'm not clear as to the real life implications when the going gets tough. Any ideas?

That would be a lot like jumping out of the frying pan and directly into the FIRE.

The Edge/MKX is a base FWD and therefore only a F/awd. Absent TC a rather DANGEROUS vehicle for operation in the wintertime or on any adverse, low traction, roadbed. Loss if traction, front wheelspin/slip, is such a DIRE matter on a FWD or F/awd vehicle that TC MUST be tuned to react INSTANTLY, fully dethrottling the engine, moderately braking the front wheels, all the while engaging the rear drive coupling if it was not already. The rear drive coupling is normally only engaged during acceleration from a stop or from a low speed when it is most probable that traction will be lost due to engine drive torque.

Forever and a day it has been 4WD/4X4 "gospel" that the "opposite' drive should NEVER be engaged on a highly tractive surface and certainly not so when turning, turning tightly at low speed especially.

The Edge/MKX F/awd system is designed to VIOLATE both of these "gospels".

WHY..??

Loss of traction on the front wheels of ANY vehicle is to be considered, should be considered, a HIGHLY SERIOUS matter, and these days that's exactly what the manufacturers are doing.

My '01 F/awd RX300, operating on perfectly dry pavement, will INSTANTLY dethrottle the engine via EFI fuel starvation if I try to accelerate into a tight turn from a stop or from a low speed. Otherwise the traction coefficient required of the front tires, acceleration torque combined with lateral forces, might well exceed their ability.

TC on a RWD or R/awd vehicle will only do that if rear traction is actually lost, rear wheelspin/slip is detected...AND the driver doesn't quickly react by feathering the gas feed.

The biggest, and most important thing, is to have the knowledge and skill to drive on the snow. All the 4 wheel drives and all wheel drives in the world won't do diddly if you don't have the skill.

Knowledge and skill is of no help with FWD and F/awd vehicles.

With RWD or R/awd when a drive wheel slips it is predominantly the rear and an experienced and skilled driver will have an opportunity to react, feather the gas, and then if necessay use the remaining traction at the front wheels to crank in some corrective stearing. With FWD or F/awd TC, Traction Control, MUST be tuned to react INSTANTLY since the driver has just lost all control ability.

That's why there was such a great public outcry which resulted in Toyota adding a TC off capability. The bad news is that apparently lots of "know it all" drivers are leaving TC off constantly...bad, BAD idea.

I just traded in a 2005 Jeep Liberty with Part Time 4WD for an Edge AWD.

The Liberty was great in the snow but defaulted to RWD when the 4WD wasn't locked in making it not so great on light snow or slush when I couldn't lock in 4WD.

This is my first AWD and from what I am reading, I should like the Edge better.

Anyone care to validate my purchase?

Thanks

I thought the Jeep Liberity was a FWD base.

Safer than FWD if all variables are the same.

The way I drive is how I drive. No matter what vehicle I am I always drive for conditions.

No over-confidence thus a greater safety factor for me.

No assurance can ever be 100%.

"...I always drive for conditions..."

That would mean, like me ('01 F/awd RX300), your FWD or F/awd vehicle gets left in a nice warm garage in foul weather or on the expectation of foul weather.

If you are driving a FWD or F/awd in wintertime conditions then you are either over-confidence in your own driving abilities and/or simply do not understand the shortcomings of those vehicles insofar as safety is concerned.

But I suppose "dead slow" and a good set of tire chains on the rear would be okay.

As the old saying goes:

There are BOLD pilots and there are OLD pilots...

But there are NO BOLD OLD pilots.

LOL. Love this intense debate. As an extreme auto guy, I will have to add my 2 cents in to this topic. I have lived between the Northwest and Northcentral part of the U.S. for life (again, many many years) near the Canadian border in easily some of the most brutal winters this country has to offer. I know this may touch a nerve with some, but it is a fact: If you cannot drive with FWD you should not be on the road. If you need the personal 'feel better' purchase of the AWD for the large sum of $2000 plus, that is perfectly acceptable. However, AWD does very little in improving driving ability of a vehicle over a FWD vehicle. You need to drive for the conditions. AWD might help you get rolling a second or two earlier from a stoplight or a stopped position, but that is about it. $2000 for this feature is a major upsell by the auto industry similar to how concession stands at movie theatres upsell popcorn and soft drinks. A great 'feel good' feature, but certainly not respectable to the price for the product.

 

 

4WD vehicles..... certainly yes.... very worth the money.

 

This is the statement wherein you sort of went awry. All AWD vehicles are NOT derived from a FWD base. Many R/awd vehicles in the market today are easily the equivalent of "4WD" vehicles. Their only "shortcoming", for some, would be the lack of 4-lo.

 

AWD (F/awd) vehicles... 100 percent not worth it unless money is no object and $2000 can be thrown around with no hesitation.

 

The SH-AWD system being the sole exception IMMHO.

 

As for resale, nope. AWD will do for resale value the same as FWD will do for resale.....

 

This is where you go wrong yet again. The same marketing "upsell" method, thinking, under which the initial owner purchased a F/awd vehicle will also apply to subsequent purchasers.

 

book value of the vehicle at time of sale or trade in respect to price paid for vehicle at at initial purchase. AWD is NOT going to give you some magic increase in value over other FWD vehicles. You paid more for that feature when buying it so you might get a little more when trading it. I have owned a couple AWD vehicles most recently my last 2008 Ford Edge (wife wanted the AWD). After loving the Edge for 2 years we have traded it for a new 2010 Ford Edge FWD. We have noticed absolutely NO improvements in handling. The FWD performs just as nice as our AWD did, other than being able to start at one or two split seconds earlier from a stopped position in extremely icy conditions. My wife is a very conservative and nervous driver (and yes we have small children that ride in it) and even she admitted there isn't any difference at all from our previous AWD Edge and our new FWD Edge. She finally believes me that we didn't need to waste the $2000 on the AWD upsell feature and are happy to use that huge amount of money towards other great things. Also, a few miles per gallon less driving and a huge probability of additional maintenance problems/costs for the AWD mechanical system just no way in heck it's worth it. The good thing about upsells though, is that they are available to those that need the 'feel good' feature and have lots of extra money to spend.

I wish you knew how to make paragraphs because that would make your posts easier to read and comprehend.

 

In your initial post you stated.

 

"AWD might help you get rolling a second or two earlier from a stoplight or a stopped position, but that is about it. $2000 for this feature is a major upsell by the auto industry similar to how concession stands at movie theatres upsell popcorn and soft drinks. A great 'feel good' feature, but certainly not respectable to the price for the product. 4WD vehicles..... certainly yes.... very worth the money. AWD vehicles... 100 percent not worth it unless money is no object and $2000 can be thrown around with no hesitation."

 

If you know anything at all about AWD systems and how they work you wouldn't be calling this "feature" as an "upsell" the auto industry.

 

I too have lived in some of the worst weather conditions being though I live in the Chicago area.

I have seen as much as 18" on one calender day. Believe me FWD wouldn't get you anywhere on a day like that. True AWD is not needed 100% of time and that is why the Ford Edge is equiped with On-Demand AWD system. The MPG difference is minimal between the FWD and AWD models. You might see a 1-2MPG gain dependent on your driving style.

 

So an "upsell" I think not. More so the assurance that my family and I will have a greater chance of getting out of that snow storm or safer in that torrential rainfall.

 

You might want to look into Part-time 4WD and Systems that use a center differential like Audi's Permanent asymmetric four-wheel drive.

Personally I think that both of you have some things right and some things WRONG.

First, in comparison to a RWD or R/awd vehicle there is NO such thing as a safe FWD or F/awd in wintertime conditions, adverse, poor tarction, roadbed conditions.

Most F/awd systems in the market today are a simple "upsell" and offer no more road-going ability or safety then their FWD "brotheren".

"..More so the assurance..."

FALSE assurance..!!

Probably even a lower safety factor than the FWD version due to the over-confidence gained from what is actually a mostly NON-FUNCTIONAL F/awd system.

The single exception IMMHO is the Acura SH-AWD system.

my 2 cents:

 

I am one of the chosen few with a job title that has "essential services" in teeny letters below it. Having driven RWD and FWD when we chose to buy our Edge there was not much debate. After a couple of really bad winters, the next vehicle would either be 4WD or AWD. Not much is going to slow down AWD with 4 snow tires on it.

That depends, depends GREATLY, on the manufacturer's definition of AWD. If you mean SH-AWD or almost any R/awd system, then fine.

I think there is no doubt that a skilled driver in a FWD can do as well if that better than a less skilled driver in an AWD, but I think there is also no doubt that an AWD system is far superior system given the same driver. So the debate is whether you want to save the money/safety because you may think that you may not need the AWD or think it is not worth the money for you. So I guess the person that needs AWD would be the person that has been in a situation where they wished they had AWD and did not.......

Some differentialtion between F/awd and R/awd is required.

The early RWD models with TRAC ('92 LS400) would start braking and dethrottling the engine the INSTANT wheelspin/slip was detected. For later models ('00 GS300) the dethrottling was delayed a few hundred milliseconds to give the driver the opportunity to "feather" the throttle to a level wherein drive torque could be sustained at a level cognizant with the roadbed traction coefficient.

Therein lies the SECRET to driving on the slippery stuff. Either there is enough traction, overall traction, to get the vehicle moving forward or there is not. The SECRET part is the driver having the ability to learn, learn quickly and in real time, the traction coefficient of the roadbed surface. You learn to EASE the throttle, trial and error, right up to the point of loss of traction but not beyond.

This is the FRUSTRATING part of many RWD and R/awd TRAC systems but ALL FWD or F/awd TRAC systems.

When TRAC reacts instantly with engine detrottling, as well it must with FWD and F/awd vehicles, there is NO opportunity for the driver to learn to manage the drive torque. The only option is to have the ability to disable TRAC altogether.

LOL. Love this intense debate. As an extreme auto guy, I will have to add my 2 cents in to this topic. I have lived between the Northwest and Northcentral part of the U.S. for life (again, many many years) near the Canadian border in easily some of the most brutal winters this country has to offer. I know this may touch a nerve with some, but it is a fact: If you cannot drive with FWD you should not be on the road. If you need the personal 'feel better' purchase of the AWD for the large sum of $2000 plus, that is perfectly acceptable. However, AWD does very little in improving driving ability of a vehicle over a FWD vehicle. You need to drive for the conditions. AWD might help you get rolling a second or two earlier from a stoplight or a stopped position, but that is about it. $2000 for this feature is a major upsell by the auto industry similar to how concession stands at movie theatres upsell popcorn and soft drinks. A great 'feel good' feature, but certainly not respectable to the price for the product. 4WD vehicles..... certainly yes.... very worth the money. AWD vehicles... 100 percent not worth it unless money is no object and $2000 can be thrown around with no hesitation. As for resale, nope. AWD will do for resale value the same as FWD will do for resale..... book value of the vehicle at time of sale or trade in respect to price paid for vehicle at at initial purchase. AWD is NOT going to give you some magic increase in value over other FWD vehicles. You paid more for that feature when buying it so you might get a little more when trading it. I have owned a couple AWD vehicles most recently my last 2008 Ford Edge (wife wanted the AWD). After loving the Edge for 2 years we have traded it for a new 2010 Ford Edge FWD. We have noticed absolutely NO improvements in handling. The FWD performs just as nice as our AWD did, other than being able to start at one or two split seconds earlier from a stopped position in extremely icy conditions. My wife is a very conservative and nervous driver (and yes we have small children that ride in it) and even she admitted there isn't any difference at all from our previous AWD Edge and our new FWD Edge. She finally believes me that we didn't need to waste the $2000 on the AWD upsell feature and are happy to use that huge amount of money towards other great things. Also, a few miles per gallon less driving and a huge probability of additional maintenance problems/costs for the AWD mechanical system just no way in heck it's worth it. The good thing about upsells though, is that they are available to those that need the 'feel good' feature and have lots of extra money to spend.

"..brutal winters.."

Cut Bank comes IMMEDIATELY to mind.

The MAJOR problem with RWD occurs when an inexperienced driver or "boy-racer" applies to much throttle for roadbed conditions.

The MAJOR problem with FWD occurs when an inexperienced driver......

The SECONDARY problem with RWD is the lack of QUICK corrective action on the part of the driver once the rear starts coming around.

The SECONDARY problem with FWD is the lack of the ABILITY for quick corrective action.

The RWD vehicle in this instance remains with the ability for directional control. Loss of traction on a FWD also means the loss of directional control.

Because of this FWD "trait" it was once though that ~200HP would be the limit for FWD vehicles.

But then it was decided that engine detuning/derating could be imposed via firmware at low speeds to avoid the issue. That practice continues today, sometimes driver selective, sometimes not.

Next came the F/awd "solution", distribute the engine torque across all four wheels as long as the surface can sustain such.

Then TRAC was added for instances wherein traction could not sustain.

The latest form(***) of F/awd only engages the rear driveline when accelerating for a stop or from a low speed.

*** Ford Escape, Mariner, Edge, etc. Mazda CX-7, etc. Toyota Venza, 2010 RX350.

Apparently you CANNOT make a silk purse from a sow's ear.

The closest would be the Acura SH-AWD system with the ability to apportion torque F/R 30/70.

Otherwise you need to ONLY consider base RWD vehicles, R/awd, if you want "drive" and directional control.

But yes, a FWD with VSC/TRAC will be just as adequate(***1) in the proper hands as almost (SH-AWD) any F/awd vehicle.

***1 Frustratingly adequate as TRAC will often activate in conditions wherein otherwise your life would be at risk. Wheelspin/slip of the front wheels is considered a rather dire, UNSAFE, situation, recovery of directional control becomes of the UTMOST importance. So FULL TRAC activation is INSTANTANEOUS, braking and engine dethrottling.

and engine dethrottling.

If you run slightly different, lower circumference, tires on the front vs the rear during the winter months the automatic engagement of the rear driveline will have the ability for rear torque biasing beyond 50/50. 40/60 or maybe even 30/70.

Much safer, like the Acura SH-AWD system, wintertime operation.

I am of the quite firm belief that the use of the rear drive is causing the PTU, PTU lubrication, to overheat.

I'm pretty sure that Ford has solved this problem in the more current models by simply relaxing the firmware specifications for the use of the rear drive coupling. If you are having problems with earlier models then the best fix procedure is to add an inline switch to the reardrive coupling clutch electric clutch. Leave the circuit open unless you are on aderse roadbed conditions. Personally I would even go so far as to be able to open the circuit when F/awd functionality is needless and fullyv close the circuit to a SOLID 12 volt source when it is needed.

You would have to be very CAREFUL in remembering to open the circuit on highly tractive surfaces.

I do not own ANY form of this F/awd technique, all I say in that regard is from book-learning.

That's a good news hopefully that's true.....I notice most of the problems were on 07s and some 08s.

While Mazda, in the CX-7 at least, added cooling to the PTO to combate the overheating problem it appears Ford simply relaxed the standards/specifications for F/awd functionality using firmware revisions. Reduce the "average" coupling level to the rear driveline thereby reducing the amount of driveline windup and/or tire scrubbing and the overheat issue is abated. Oh, while you're in there eliminate the driver's ability to "lock" the system in F/awd mode.

First, substantially raise the federal tax on public roadway use fuels. Then advise ALL manufacturers that they must provide a custom engine firmware control REFLASH at the request of the owner/buyer.

The reflash would be designed to LIMIT the 0-60MPH time to something reasonable considering the weight of the vehicle. The heavier the vehicle the longer it would take to accelerate from a stop to 60MPH, regardless of actual engine HP. Passing HP, say from 35MPH and up, and subsequent to a period of cruise, would NOT be throttled.

Many modern FWD or F/awd vehicles are already doing this, limiting engine torque in the low gear ranges, as a safety matter.

A rebate program would reward those who volunteerily had the reflash done by the dealer.

Vehicles that already met the new 0-60MPH standard would automatically be eligble for the rebate program. My '93 Ford Ranger PU w/I4/stick for instance.