Pulling the PTU Fuse
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Re: Pulling the PTU Fuse
It might be a little less that a real FWD because of the extra weight covered.
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Re: Pulling the PTU Fuse
While Ford might like to market as such the modern day FE/FEH it is NOT a 4WD vehicle, FAR from it. The early FE's had a true 4WD system which the driver could engage *****-nilly, although advised not to do so except on a low traction surface.
As time progressed and the failure rates of these original 4WD systems got out of hand a temperature sensor was added to the rear coupling clutch along with an indicator to advise the driver that the rear clutch was beginning to overheat. If the driver for some reason continued to "abuse" the system and the temperature continued to rise the 4WD system would be disabled and the driver was advised (forced to..?) to pull over long enough to cool the system off.
Obviously none of this worked, drivers (like Bill..??) continued to abuse the drive system, and most likely insisted that the resulting need for repairs be covered under the warranty. So Ford discontinued the FE's 4WD system in favor of todays A/F/awd, Automatic Front BIASED All-Wheel Drive system.
IMMHO unless the driver has the ability to somehow manually engage the drive wheels "opposite" to the HARD coupled/driven wheels, the vehicle CANNOT be referred to as being 4WD.
Automatic AWD would be much more acceptable, more definitive to the general automotive buying public. And as you can see it is also my belief that a further definitive descriptor should be used for these newer awd system designs, F/awd, R/awd.
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Re: Pulling the PTU Fuse
wptski: It isn't that simple. 4WD vehicles get lower mileage for a reason. They have more driveline friction to overcome. The reason that 4WD vehicles have locking hubs on the front axle is to reduce that friction when 2WD is all that's needed.
Hence my remark on the 1-2 mpg on a jeep I once used. The driveline friction is reduced when the hubs are unlocked and the differential & propeller shaft don't rotate.
My point in the FEH case is that the active torque coupling does not disconnect any part of the driveline in the sense of reducing driveline friction. All elements of the driveline continue to rotate at full speed for the conditions of the vehicle.
The Active torque coupling only interconnects the front and rear axles based on the commanded signal to split torque between the axles as needed.
Hence the issue of driveline friction is moot: it all rotates at virtually the same speed regardless of the commanded signal (or lack thereof with the fuse pulled) to the active torque coupling.
Hence my remark on the 1-2 mpg on a jeep I once used. The driveline friction is reduced when the hubs are unlocked and the differential & propeller shaft don't rotate.
My point in the FEH case is that the active torque coupling does not disconnect any part of the driveline in the sense of reducing driveline friction. All elements of the driveline continue to rotate at full speed for the conditions of the vehicle.
The Active torque coupling only interconnects the front and rear axles based on the commanded signal to split torque between the axles as needed.
Hence the issue of driveline friction is moot: it all rotates at virtually the same speed regardless of the commanded signal (or lack thereof with the fuse pulled) to the active torque coupling.
Imported from Detroit
Joined: Apr 2009
Posts: 1,051
From: Michigan
Re: Pulling the PTU Fuse
wptski: It isn't that simple. 4WD vehicles get lower mileage for a reason. They have more driveline friction to overcome. The reason that 4WD vehicles have locking hubs on the front axle is to reduce that friction when 2WD is all that's needed.
Hence my remark on the 1-2 mpg on a jeep I once used. The driveline friction is reduced when the hubs are unlocked and the differential & propeller shaft don't rotate.
My point in the FEH case is that the active torque coupling does not disconnect any part of the driveline in the sense of reducing driveline friction. All elements of the driveline continue to rotate at full speed for the conditions of the vehicle.
The Active torque coupling only interconnects the front and rear axles based on the commanded signal to split torque between the axles as needed.
Hence the issue of driveline friction is moot: it all rotates at virtually the same speed regardless of the commanded signal (or lack thereof with the fuse pulled) to the active torque coupling.
Hence my remark on the 1-2 mpg on a jeep I once used. The driveline friction is reduced when the hubs are unlocked and the differential & propeller shaft don't rotate.
My point in the FEH case is that the active torque coupling does not disconnect any part of the driveline in the sense of reducing driveline friction. All elements of the driveline continue to rotate at full speed for the conditions of the vehicle.
The Active torque coupling only interconnects the front and rear axles based on the commanded signal to split torque between the axles as needed.
Hence the issue of driveline friction is moot: it all rotates at virtually the same speed regardless of the commanded signal (or lack thereof with the fuse pulled) to the active torque coupling.
Here's a case where if you use 4WD with auto-lockers very seldom, they have a habit of sticking.
If you drive a manual shift, are in 4WD, shift into reverse, rolling backwards with the clutch in the auto-lockers sense no torque and unlock. Worse yet like one of my Rangers would unlock on one side only which is hard on the differential.
I had a '97 Ranger with auto-locking hubs but it seems that even the '97 F-150 didn't. The following is from the '97 F-150 manual describing the shift on the fly.
Electronic Shift On the Fly (ESOF) Operation
The ESOF system is an electronic shift 4x4 system that allows the operator to choose between two different 4x4 modes as well as 2-wheel drive. The operator can switch between 2WD and 4WD HIGH mode at speed. To engage or disengage LOW Range, the vehicle speed must be less than 5 kph, the brake depressed, and the transmission must be in NEUTRAL.
The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is used to spin up the front driveline when shifting from 2WD to 4x4 High mode at speed. When the control switch on the instrument panel is turned, the generic electronic module (GEM) recognizes that a shift has been requested and activates the electromagnetic clutch and the relays which power the transfer case shift motor. When the shift motor reaches the desired position as determined by the contact plate position inputs to the GEM, power to the shift relays and motors will be removed. When the transfer case front and rear output shafts are synchronized, the spring loaded lockup collar mechanically engages the mainshaft hub to the drive sprocket. Finally, the front axle collar is engaged and the electromagnetic clutch is deactivated
Last edited by wptski; Aug 26, 2010 at 05:01 PM.
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Re: Pulling the PTU Fuse
wptski: It isn't that simple. 4WD vehicles get lower mileage for a reason. They have more driveline friction to overcome. The reason that 4WD vehicles have locking hubs on the front axle is to reduce that friction when 2WD is all that's needed.
Hence my remark on the 1-2 mpg on a jeep I once used. The driveline friction is reduced when the hubs are unlocked and the differential & propeller shaft don't rotate.
If the differential and propeller shaft don't rotate then why would you need a means to unlock them form the hubs..? If you have a "means" for preventing the propeller shaft and the differential from rotating what would unlocking the hubs accomplish..?
My point in the FEH case is that the active torque coupling does not disconnect any part of the driveline in the sense of reducing driveline friction. All elements of the driveline continue to rotate at full speed for the conditions of the vehicle.
Yes, all elements of the drive train continue to rotate but with no torque loading to provide the additional stress and friction that would be present were the rear drive coupling engaged.
The Active torque coupling only interconnects the front and rear axles based on the commanded signal to split torque between the axles as needed.
Hence the issue of driveline friction is moot: it all rotates at virtually the same speed regardless of the commanded signal
No, that's where you missing the boat. If the commanded signal is, say, 30% then any torque loading to/on/from the rear drive system exceeding that level would be permitted via internal slippage of the rear coupling clutches. You said it yourself earlier.
(or lack thereof with the fuse pulled) to the active torque coupling.
Hence my remark on the 1-2 mpg on a jeep I once used. The driveline friction is reduced when the hubs are unlocked and the differential & propeller shaft don't rotate.
If the differential and propeller shaft don't rotate then why would you need a means to unlock them form the hubs..? If you have a "means" for preventing the propeller shaft and the differential from rotating what would unlocking the hubs accomplish..?
My point in the FEH case is that the active torque coupling does not disconnect any part of the driveline in the sense of reducing driveline friction. All elements of the driveline continue to rotate at full speed for the conditions of the vehicle.
Yes, all elements of the drive train continue to rotate but with no torque loading to provide the additional stress and friction that would be present were the rear drive coupling engaged.
The Active torque coupling only interconnects the front and rear axles based on the commanded signal to split torque between the axles as needed.
Hence the issue of driveline friction is moot: it all rotates at virtually the same speed regardless of the commanded signal
No, that's where you missing the boat. If the commanded signal is, say, 30% then any torque loading to/on/from the rear drive system exceeding that level would be permitted via internal slippage of the rear coupling clutches. You said it yourself earlier.
(or lack thereof with the fuse pulled) to the active torque coupling.
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Re: Pulling the PTU Fuse
Bill seems to understand and accept the FACT that a 4WD (F/awd in the current case) will have lower FE than an 2WD system, he just isn't able to fully "reason" as to why that is the case.
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Re: Pulling the PTU Fuse
You seem more interested in showing off your knowledge than in understanding the issue of driveline frictional components. Didn't ask for a dissertation on the different kinds of locking hubs.
FYI The auto engage front axle in my Suburban (the one that got an 8% increase in mpg with Amsoil over Mobil One) works just fine in all conditions as did the Warn Hubs in my old CJ.
The point here is the driveline friction in the FEH versus how it changes in other 4WD vehicles, the rest is just illustration.
Bottom line: The FEH driveline frictional components doesn't change regardless of the engagement percentage of the Torque transfer unit on the front of the rear differential.
So, if the rotating components remains constant and the only thing that pulling the fuse does is put the torque transfer unit to 0% engagement then the mpg observed should change little (if that is all that happens when the fuse is pulled).
FYI The auto engage front axle in my Suburban (the one that got an 8% increase in mpg with Amsoil over Mobil One) works just fine in all conditions as did the Warn Hubs in my old CJ.
The point here is the driveline friction in the FEH versus how it changes in other 4WD vehicles, the rest is just illustration.
Bottom line: The FEH driveline frictional components doesn't change regardless of the engagement percentage of the Torque transfer unit on the front of the rear differential.
So, if the rotating components remains constant and the only thing that pulling the fuse does is put the torque transfer unit to 0% engagement then the mpg observed should change little (if that is all that happens when the fuse is pulled).
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From: Beautiful Pacific NW
Re: Pulling the PTU Fuse
You seem more interested in showing off your knowledge than in understanding the issue of driveline frictional components. Didn't ask for a dissertation on the different kinds of locking hubs.
FYI The auto engage front axle in my Suburban (the one that got an 8% increase in mpg with Amsoil over Mobil One) works just fine in all conditions as did the Warn Hubs in my old CJ.
The point here is the driveline friction in the FEH versus how it changes in other 4WD vehicles, the rest is just illustration.
Bottom line: The FEH driveline frictional components doesn't change regardless of the engagement percentage of the Torque transfer unit on the front of the rear differential.
Did you really mean to say "..frictional components doesn't change..", or did you mean "frictional component doesn't change.."...?
I'm rather sure you understand that the frictional component, "amount of friction" of the driveline components always increases with increasing, increased torque coupling. Our tires wouldn't wear out if the frictional component remained the same underway as when stationary.
So, if the rotating components remains constant and the only thing that pulling the fuse does is put the torque transfer unit to 0% engagement then the mpg observed should change little (if that is all that happens when the fuse is pulled).
FYI The auto engage front axle in my Suburban (the one that got an 8% increase in mpg with Amsoil over Mobil One) works just fine in all conditions as did the Warn Hubs in my old CJ.
The point here is the driveline friction in the FEH versus how it changes in other 4WD vehicles, the rest is just illustration.
Bottom line: The FEH driveline frictional components doesn't change regardless of the engagement percentage of the Torque transfer unit on the front of the rear differential.
Did you really mean to say "..frictional components doesn't change..", or did you mean "frictional component doesn't change.."...?
I'm rather sure you understand that the frictional component, "amount of friction" of the driveline components always increases with increasing, increased torque coupling. Our tires wouldn't wear out if the frictional component remained the same underway as when stationary.
So, if the rotating components remains constant and the only thing that pulling the fuse does is put the torque transfer unit to 0% engagement then the mpg observed should change little (if that is all that happens when the fuse is pulled).
No work, no driveline windup, no tire scrubbing, less overall frictional heating, etc, IMPROVED FE.
Imported from Detroit
Joined: Apr 2009
Posts: 1,051
From: Michigan
Re: Pulling the PTU Fuse
You seem more interested in showing off your knowledge than in understanding the issue of driveline frictional components. Didn't ask for a dissertation on the different kinds of locking hubs.
FYI The auto engage front axle in my Suburban (the one that got an 8% increase in mpg with Amsoil over Mobil One) works just fine in all conditions as did the Warn Hubs in my old CJ.
The point here is the driveline friction in the FEH versus how it changes in other 4WD vehicles, the rest is just illustration.
Bottom line: The FEH driveline frictional components doesn't change regardless of the engagement percentage of the Torque transfer unit on the front of the rear differential.
So, if the rotating components remains constant and the only thing that pulling the fuse does is put the torque transfer unit to 0% engagement then the mpg observed should change little (if that is all that happens when the fuse is pulled).
FYI The auto engage front axle in my Suburban (the one that got an 8% increase in mpg with Amsoil over Mobil One) works just fine in all conditions as did the Warn Hubs in my old CJ.
The point here is the driveline friction in the FEH versus how it changes in other 4WD vehicles, the rest is just illustration.
Bottom line: The FEH driveline frictional components doesn't change regardless of the engagement percentage of the Torque transfer unit on the front of the rear differential.
So, if the rotating components remains constant and the only thing that pulling the fuse does is put the torque transfer unit to 0% engagement then the mpg observed should change little (if that is all that happens when the fuse is pulled).
You brought up the auto-locking hubs which might not be used anymore.
What's a auto engaged front axle? What kind of hubs?
Warn hubs? Used with a manually operated 4WD system?
Why are you talking about Amsoil and Mobil One oil now?
One '08 FEH owner here reported a 2mpg increase after pulling the fuse.
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Re: Pulling the PTU Fuse
Oops, two Bills.
Wptski:
Insofar as FE is concerned the rear driveline is automatically engaged at the worse of times, while the best of times insofar as traction is concerned.
The "automatic" rear drive is engaged, productively engaged (potentially), ONLY when the "engine" is working at its hardest, during acceleration or times of heavy loading. Obviously that would also be the times that the adverse affects of tire scrubbing and/or driveline windup would result in the greatest negative effects on FE.
Sorry if I have used "Bill" inappropriately a few times.
The first engineer to discover a method for determining the traction coefficient of a roadbed in real time will undoubtedly win the lottery.
Wptski:
Insofar as FE is concerned the rear driveline is automatically engaged at the worse of times, while the best of times insofar as traction is concerned.
The "automatic" rear drive is engaged, productively engaged (potentially), ONLY when the "engine" is working at its hardest, during acceleration or times of heavy loading. Obviously that would also be the times that the adverse affects of tire scrubbing and/or driveline windup would result in the greatest negative effects on FE.
Sorry if I have used "Bill" inappropriately a few times.
The first engineer to discover a method for determining the traction coefficient of a roadbed in real time will undoubtedly win the lottery.
