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

"..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.

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.

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

"..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".

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.

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

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 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.

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.

"...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.

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.

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.

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 thought the Jeep Liberity was a FWD base.

"...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.

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.

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

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.

"..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.

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.