Pulling the PTU Fuse
Imported from Detroit
Joined: Apr 2009
Posts: 1,051
From: Michigan
Re: Pulling the PTU Fuse
"I don't keep a database of who has what. If you indeed have the manuals, you have the info at hand that states that the PTU is powered all the time. Your OP implies that you don't understand this fact or somehow you think the FEH is different, it isn't unless the Ford manual is wrong."
wptski: We've interacted enough for you to know...
Stop such behavior, it's self aggrandizing. Of course it's powered all the time, unless one pulls the fuse, which is the issue at hand, or did you miss that in the title?
wptski: We've interacted enough for you to know...
Stop such behavior, it's self aggrandizing. Of course it's powered all the time, unless one pulls the fuse, which is the issue at hand, or did you miss that in the title?
Either read your manual or Post #19.
Ridiculously Active Enthusiast
Joined: Sep 2006
Posts: 1,678
From: Beautiful Pacific NW
Re: Pulling the PTU Fuse
"I don't keep a database of who has what. If you indeed have the manuals, you have the info at hand that states that the PTU is powered all the time. Your OP implies that you don't understand this fact or somehow you think the FEH is different, it isn't unless the Ford manual is wrong."
wptski: We've interacted enough for you to know...
Stop such behavior, it's self aggrandizing. Of course it's powered all the time, unless one pulls the fuse, which is the issue at hand, or did you miss that in the title?
wptski: We've interacted enough for you to know...
Stop such behavior, it's self aggrandizing. Of course it's powered all the time, unless one pulls the fuse, which is the issue at hand, or did you miss that in the title?
Anytime the front wheels are being driven, "torqued", the pto/ptu is "powered", fuse or switch to the rear clutch be dammed.
Thread Starter
|
Ridiculously Active Enthusiast
Joined: Jan 2009
Posts: 863
Re: Pulling the PTU Fuse
Talk about unproductive...
You guys have completely missed the point: what is the experience of people with pulling the PTU fuse? Is there a relation between pulling the PTU fuse and PTU failures?
Go away, please, you're distracting people.
You guys have completely missed the point: what is the experience of people with pulling the PTU fuse? Is there a relation between pulling the PTU fuse and PTU failures?
Go away, please, you're distracting people.
Last edited by Bill Winney; Aug 24, 2010 at 05:01 AM.
Imported from Detroit
Joined: Apr 2009
Posts: 1,051
From: Michigan
Re: Pulling the PTU Fuse
The fuse disables the 4WD module which controls the ATC electric clutch in the rearend. The driveshaft still rotates driven by PTU. As far as luberication goes, removing the fuse has no effect on that but it does eliminate the PTU's load.
Last edited by wptski; Aug 24, 2010 at 01:13 PM.
Ridiculously Active Enthusiast
Joined: Sep 2006
Posts: 1,678
From: Beautiful Pacific NW
Re: Pulling the PTU Fuse
Run 10 vehicles for each oil type >100,000 miles and in the end you might have a definitive answer, but more likely not. That is to say that there is no short term answer to you question ever assuming the PTO/PTU itsself were to be switched on-and-off. Given teh high quality/performance of ALL engine lubricating oils these days it might take 500,000 miles on each test vehicle before a definitive answer could be had.
My '01 911/996 C4 has a modification that allows me to disable the A/C, something I do rather religiously except for times actual cabin cooling is needed. Will that extend the life of the A/C compressor?? Logically it certainly should but I'd be the last to place a bet on the issue...?
Admittently the FE/FEH PTO/PTU is a different story in that they are clearly subject to premature failures as shipped from the factory. So, here we are again, logically and with certainty one would think unloading the PTO/PTU by removing the rear clutch electrical power would extend the life of same, NOT shorten the service life or have any adverse effect on the PTO/PTU itsself in any way.
But NONE of us, including me, would place a substantial amount of money on the issue, one way or another. Would I "bet" by doing the modification to my own FEH were I to own one.....YOU BET, even absent the premature failure issue. It is just SIMPLY wrong, really poor design engineering, to have any level of locking F/R when turning. From my personal standpoint I would much rather have the engine output torque automatically LIMITED the more the lateral forces build as I turn as many FWD and F/awd vehicles now do.
On the other hand my procedure, were I to ever own a F/awd system of this type, Sienna, Venza, RX350, Highlander(??), 2012 restyled FEH, would be to supply a permanent 12 volts to the rear drive clutch and remove a front halfshaft to convert the vehicle to RWD, ONLY RWD.
Probably even add a manual coupling/uncoupling device ("TOAD MODE") to the front halfshaft so that I could have TRUE/PART-TIME 4WD when/if the need arose.
Last edited by wwest; Aug 24, 2010 at 07:32 AM.
Thread Starter
|
Ridiculously Active Enthusiast
Joined: Jan 2009
Posts: 863
Re: Pulling the PTU Fuse
After all is said & done, the PTU is nothing but a 90º angle drive.
It is therefore quite likely very sensitive to slight angular misalignments. Hence the failure rates. Now the large (I believe aluminum) coupling with very long bolts on the front of the propeller shaft makes sense: it is to ensure slight misalignments don't cause excessive wear within the PTU.
All components are rotating all the time in the PTU, so pulling the fuse is irrelevant to its lubrication.
The coupling-decoupling occurs in the Active Torque Coupling on the front of the rear differential. All elements of the driveline are rotating all the time. So there is no reduction in rotating elements by pulling the fuse. This means that there is no reduction in friction that has to be overcome by the engine.
So we need to figure out another reason that pulling the fuse causes an increase in fuel mileage.
It is therefore quite likely very sensitive to slight angular misalignments. Hence the failure rates. Now the large (I believe aluminum) coupling with very long bolts on the front of the propeller shaft makes sense: it is to ensure slight misalignments don't cause excessive wear within the PTU.
All components are rotating all the time in the PTU, so pulling the fuse is irrelevant to its lubrication.
The coupling-decoupling occurs in the Active Torque Coupling on the front of the rear differential. All elements of the driveline are rotating all the time. So there is no reduction in rotating elements by pulling the fuse. This means that there is no reduction in friction that has to be overcome by the engine.
So we need to figure out another reason that pulling the fuse causes an increase in fuel mileage.
Ridiculously Active Enthusiast
Joined: Sep 2006
Posts: 1,678
From: Beautiful Pacific NW
Re: Pulling the PTU Fuse
After all is said & done, the PTU is nothing but a 90º angle drive.
It is therefore quite likely very sensitive to slight angular misalignments. Hence the failure rates. Now the large (I believe aluminum) coupling with very long bolts on the front of the propeller shaft makes sense: it is to ensure slight misalignments don't cause excessive wear within the PTU.
All components are rotating all the time in the PTU, so pulling the fuse is irrelevant to its lubrication.
The coupling-decoupling occurs in the Active Torque Coupling on the front of the rear differential. All elements of the driveline are rotating all the time. So there is no reduction in rotating elements by pulling the fuse. This means that there is no reduction in friction that has to be overcome by the engine.
So we need to figure out another reason that pulling the fuse causes an increase in fuel mileage.
It is therefore quite likely very sensitive to slight angular misalignments. Hence the failure rates. Now the large (I believe aluminum) coupling with very long bolts on the front of the propeller shaft makes sense: it is to ensure slight misalignments don't cause excessive wear within the PTU.
All components are rotating all the time in the PTU, so pulling the fuse is irrelevant to its lubrication.
The coupling-decoupling occurs in the Active Torque Coupling on the front of the rear differential. All elements of the driveline are rotating all the time. So there is no reduction in rotating elements by pulling the fuse. This means that there is no reduction in friction that has to be overcome by the engine.
So we need to figure out another reason that pulling the fuse causes an increase in fuel mileage.
What, WHAT...????
Operate a simple floor jack with a load and then with a serious load. Can you really say the floorjack bearings weren't under a more serious load in teh latter case..? If so then come back and tell me that there is no reduction in driveline friction/windup, tire scrubbing, when the rear clutch coupling fuse is pulled.
My step-son installed tire chains (required) on the front of his F/awd Chrysler T&C on the way to skiing a few years ago. The Chrysler's PTO/PTU lasted less than 20-25 miles before going TU. The T&C uses a VC, Viscous clutch, to "sense" wheelspin/slip and "tighten" the torque coupling to the rear. The tire chains ONLY on the front made it seem as if the wheelspin/slip was CONSTANT/continuous so the VC responded accordingly.
And it isn't just drive or acceleration load, even the smallest disparity in average, combined L/R, F/R tire circumference will increase the level of torque loading of the PTO/PTU, turn the front wheels slightly and the driveline windup and tire scrubbing torque loading of the PTO/PTU increases dramatically. IMMHO it was/is the ultimate in design stupidity for the FE/FEH to maintain a substantial level of coupling to the rear as you turn. But then the alternative was/is to automatically dethrottle, limit the engine torque, as the turn rate rises. So until the stability system was adopted by the FE/FEH to automatically add braking and dethrottle the engine if front traction was lost during a turn I guess the Ford engineers made the best choice.
Speaking of which, pulling the fuse would not only raise FE via reducing the torque loading of the drive train, but it would also extend the tire life to a measureable extent.
And of course we already know the service life of the PTO/PTU would be extended accordingly.
Last edited by wwest; Aug 26, 2010 at 09:16 AM.
Thread Starter
|
Ridiculously Active Enthusiast
Joined: Jan 2009
Posts: 863
Re: Pulling the PTU Fuse
wwest, usually I leave your posts unread as you're on my ignore list...
But you do provide comic relief every once in a while.
For example: pulling the fuse doesn't reduce the total torque loading on the drive train, it just shifts where its seen.
The value of locking hubs in a 4WD vehilce is that you don't expend gas in two wheel drive rolling the front drive line and differential. On an old Jeep I once owned it was good for about 1-2 mpg. But that's not what's going on here. Everything keeps rolling.
Also driveline windup does not happen as you seem to think. The wheel to wheel windup is taken care of in the differential and the front to rear windup is taken care of in the active torque coupling.
But you do provide comic relief every once in a while.
For example: pulling the fuse doesn't reduce the total torque loading on the drive train, it just shifts where its seen.
The value of locking hubs in a 4WD vehilce is that you don't expend gas in two wheel drive rolling the front drive line and differential. On an old Jeep I once owned it was good for about 1-2 mpg. But that's not what's going on here. Everything keeps rolling.
Also driveline windup does not happen as you seem to think. The wheel to wheel windup is taken care of in the differential and the front to rear windup is taken care of in the active torque coupling.
Ridiculously Active Enthusiast
Joined: Sep 2006
Posts: 1,678
From: Beautiful Pacific NW
Re: Pulling the PTU Fuse
After all is said & done, the PTU is nothing but a 90º angle drive.
It is therefore quite likely very sensitive to slight angular misalignments. Hence the failure rates. Now the large (I believe aluminum) coupling with very long bolts on the front of the propeller shaft makes sense: it is to ensure slight misalignments don't cause excessive wear within the PTU.
All components are rotating all the time in the PTU, so pulling the fuse is irrelevant to its lubrication.
The coupling-decoupling occurs in the Active Torque Coupling on the front of the rear differential. All elements of the driveline are rotating all the time. So there is no reduction in rotating elements by pulling the fuse. This means that there is no reduction in friction that has to be overcome by the engine.
So we need to figure out another reason that pulling the fuse causes an increase in fuel mileage.
It is therefore quite likely very sensitive to slight angular misalignments. Hence the failure rates. Now the large (I believe aluminum) coupling with very long bolts on the front of the propeller shaft makes sense: it is to ensure slight misalignments don't cause excessive wear within the PTU.
All components are rotating all the time in the PTU, so pulling the fuse is irrelevant to its lubrication.
The coupling-decoupling occurs in the Active Torque Coupling on the front of the rear differential. All elements of the driveline are rotating all the time. So there is no reduction in rotating elements by pulling the fuse. This means that there is no reduction in friction that has to be overcome by the engine.
So we need to figure out another reason that pulling the fuse causes an increase in fuel mileage.
Ridiculously Active Enthusiast
Joined: Sep 2006
Posts: 1,678
From: Beautiful Pacific NW
Re: Pulling the PTU Fuse
wwest, usually I leave your posts unread as you're on my ignore list...
But you do provide comic relief every once in a while.
For example: pulling the fuse doesn't reduce the total torque loading on the drive train, it just shifts where its seen.
Strange as it may seem I find myself in TOTAL agreement with the above. Given an equal rate of acceleration, say 10 seconds 0-60, the total torque laid down on the roadbed with and without the fuse would be, MUST BE, the same.
The obvious difference being the PTO/PTU wouldn't be as subject to nearly as much frictional heating and mechanical wear with the fuse removed.
Which brings us around to the poor safety factor of FWD vehicles on slippery road conditions. If the fuse is removed in those situations the ENTIRE torque level of the 10 second 0-60 acceleration rate must be laid down by the front tires'. Add in a bit of lateral force, directional change, and a slippery roadbed and if you're lucky you only spend the next few days in that hospital bed.
The value of locking hubs in a 4WD vehilce is that you don't expend gas in two wheel drive rolling the front drive line and differential. On an old Jeep I once owned it was good for about 1-2 mpg. But that's not what's going on here. Everything keeps rolling.
Sorry, but I must ask, in just what, which case does "everything" NOT keep rolling...?
Also driveline windup does not happen as you seem to think. The wheel to wheel windup is taken care of in the differential
Yes, for L/R "wheel" windup. But even there should the differential be too "forgiving", loose, TC will step in and "enforce" windup, just as would a mechanical LSD.
and the front to rear windup is taken care of in the active torque coupling.
Not so, NOT possible. The base purpose of the active torque coupling rear clutch is to ENSURE some definitive level of torque coupling to the rear driveline in situations wherein that is desireable. If the coupling level of the "moment"/instant, is 30% then the ENTIRE rear drive "link", PTO and back, will "suffer" driveline windup and tire scrubbing to that level.
But you do provide comic relief every once in a while.
For example: pulling the fuse doesn't reduce the total torque loading on the drive train, it just shifts where its seen.
Strange as it may seem I find myself in TOTAL agreement with the above. Given an equal rate of acceleration, say 10 seconds 0-60, the total torque laid down on the roadbed with and without the fuse would be, MUST BE, the same.
The obvious difference being the PTO/PTU wouldn't be as subject to nearly as much frictional heating and mechanical wear with the fuse removed.
Which brings us around to the poor safety factor of FWD vehicles on slippery road conditions. If the fuse is removed in those situations the ENTIRE torque level of the 10 second 0-60 acceleration rate must be laid down by the front tires'. Add in a bit of lateral force, directional change, and a slippery roadbed and if you're lucky you only spend the next few days in that hospital bed.
The value of locking hubs in a 4WD vehilce is that you don't expend gas in two wheel drive rolling the front drive line and differential. On an old Jeep I once owned it was good for about 1-2 mpg. But that's not what's going on here. Everything keeps rolling.
Sorry, but I must ask, in just what, which case does "everything" NOT keep rolling...?
Also driveline windup does not happen as you seem to think. The wheel to wheel windup is taken care of in the differential
Yes, for L/R "wheel" windup. But even there should the differential be too "forgiving", loose, TC will step in and "enforce" windup, just as would a mechanical LSD.
and the front to rear windup is taken care of in the active torque coupling.
Not so, NOT possible. The base purpose of the active torque coupling rear clutch is to ENSURE some definitive level of torque coupling to the rear driveline in situations wherein that is desireable. If the coupling level of the "moment"/instant, is 30% then the ENTIRE rear drive "link", PTO and back, will "suffer" driveline windup and tire scrubbing to that level.
Simply NOT the case.
