Bad PTU-Am I the first?
#21
10-01-2009, 03:05 PM
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Re: Bad PTU-Am I the first?
That's what I first thought when seeing SG-II pictures showing 47.6% rear wheel torque under good driving conditions. My testing in the link I provided aboved proved otherwise.
I'm not sure why Ford even refers to it as a "on demand" system when torque is so easily sent to the rear wheels!
That one sentence from a '09 shop manual about the 4WD system says it all: Under normal driving conditions "most" of the torque is sent to the front wheels.
I'm not sure why Ford even refers to it as a "on demand" system when torque is so easily sent to the rear wheels!
That one sentence from a '09 shop manual about the 4WD system says it all: Under normal driving conditions "most" of the torque is sent to the front wheels.
Engine torque coupling to the rear driveline in that circumstance CANNOT exceed 5%, or even that much, without quickly destroying the drivetrain. Even if you were able to drive in a perfectly straight line the variations in circumference of the tires would result in premature failure of some part of the driveline.
Coupling that much engine torque to the rear driveline under WOT conditions or even moderately hard acceleration might be acceptable (you can't "accelerate" forever) but in straight line driving, cruising, NO WAY.....and...NO NEED.
ABSOLUTELY NO NEED...!!
Engine torque
Last edited by wwest; 10-01-2009 at 03:52 PM.
#22
10-01-2009, 04:08 PM
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Re: Bad PTU-Am I the first?
I have a 2007 and have the same symptoms a low speed 0-5 mph. It is like a "surging". Took it to the dealer and they diagnosed a faulty transmission and replaced the eCVT. That did not solve the problem completely and now they are waiting for a PTU. Fortunately their doing it under warranty and gave me a loaner for the 2 weeks they had the car to replace the eCVT. Told me that it was safe to drive until they receive a PTU.
Problem is that there had been issues with leaking seals in the PTU and initially they were replacing entire PTU units, until they realized that they only needed to service the seals.
Or maybe the seals were a symptom, not directly the problem. An overheating, SERIOUSLY overheating, PTU/PTO might cause the gear oil to expand in volume enough to blow the seals. Might even BOIL the gear oil from the looks and odor of a Chrysler PTO/PTU that failed for the very same reason.
"...Only needed to service the seals.."
Once the realization came that the real problem was overheating of the PTO due to the rear driveline clutch being FULLY engaged to allow it to cool.
That has resulted in no PTU units being immediately available. It has been a week but I think it will probably take a month for the dealer to get a unit (I hope not longer).
There hardest stress I put on it is when I accelerate onto a highway, otherwise I am pretty good with it. Could this stress out the PTU?
Problem is that there had been issues with leaking seals in the PTU and initially they were replacing entire PTU units, until they realized that they only needed to service the seals.
Or maybe the seals were a symptom, not directly the problem. An overheating, SERIOUSLY overheating, PTU/PTO might cause the gear oil to expand in volume enough to blow the seals. Might even BOIL the gear oil from the looks and odor of a Chrysler PTO/PTU that failed for the very same reason.
"...Only needed to service the seals.."
Once the realization came that the real problem was overheating of the PTO due to the rear driveline clutch being FULLY engaged to allow it to cool.
That has resulted in no PTU units being immediately available. It has been a week but I think it will probably take a month for the dealer to get a unit (I hope not longer).
There hardest stress I put on it is when I accelerate onto a highway, otherwise I am pretty good with it. Could this stress out the PTU?
No, but putting the rear driveline clutch into the fully engaged mode to prevent it from being further overheated and thereby "deflecting" the driveline stress to the PTU would.
My guess would be that the PTU seals are now being replaced along with F/awd firmware revisions, relaxing the rear drive functionality, at the same time.
"..resulted in no PTU units being immediately available..."
To quote Saran Palin..."you betcha"...!!
#23
05-20-2010, 11:22 AM
Re: Bad PTU-Am I the first?
I am sad to report you are not the only. 
I had my 07 Mariner Hybrid hauled away to the dealership on a flatbed today. They just called - bad PTU.
I had my 07 Mariner Hybrid hauled away to the dealership on a flatbed today. They just called - bad PTU.
#24
05-20-2010, 02:12 PM
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Re: Bad PTU-Am I the first?
Were I the (not so proud) owner of an Escape or mariner F/awd I would pull the fuse to the rear drive coupling except when I truly needed the drive, additional traction, from the rear.
Or else find some way to water cool the PTO/PTU as has done Mazda.
Or else find some way to water cool the PTO/PTU as has done Mazda.
#25
05-20-2010, 03:45 PM
Re: Bad PTU-Am I the first?
That would stop the rear from engaging but the PTU still turns the driveshaft anyway.
#26
05-20-2010, 04:15 PM
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Re: Bad PTU-Am I the first?
Plus which the PTO failures are more likely the result of inadvertent driveline windup and/or tire scrubbing when the rear drive is engaged on a highly tractive surface, especially when turning.
Ford..IDIOTS...!!
Ford.."EcoBoost"/TwinForce/Gas-Guzzlers...IDIOTS...!!
Last edited by wwest; 05-20-2010 at 04:18 PM.
#27
05-20-2010, 07:57 PM
Re: Bad PTU-Am I the first?
But with no torque "back" resistance, no drive torque transferred to the rear, little or no heating of the PTO's "free-wheeling" ring & pinion would result.
Plus which the PTO failures are more likely the result of inadvertent driveline windup and/or tire scrubbing when the rear drive is engaged on a highly tractive surface, especially when turning.
Ford..IDIOTS...!!
Ford.."EcoBoost"/TwinForce/Gas-Guzzlers...IDIOTS...!!
Plus which the PTO failures are more likely the result of inadvertent driveline windup and/or tire scrubbing when the rear drive is engaged on a highly tractive surface, especially when turning.
Ford..IDIOTS...!!
Ford.."EcoBoost"/TwinForce/Gas-Guzzlers...IDIOTS...!!
What I should have was: That would not stop the PTU from being powered and/or the driveshaft from rotating.
Everytime one makes a turn which is generally at lower speeds, torque is sent to the rear wheels but since it's less than 50% there isn't a problem other than less MPG. If there were PTU problems, they were in the past.
#28
05-21-2010, 09:25 AM
Re: Bad PTU-Am I the first?
Whoops! Bad statement!
What I should have was: That would not stop the PTU from being powered and/or the driveshaft from rotating.
Everytime one makes a turn which is generally at lower speeds, torque is sent to the rear wheels but since it's less than 50% there isn't a problem other than less MPG. If there were PTU problems, they were in the past.
What I should have was: That would not stop the PTU from being powered and/or the driveshaft from rotating.
Everytime one makes a turn which is generally at lower speeds, torque is sent to the rear wheels but since it's less than 50% there isn't a problem other than less MPG. If there were PTU problems, they were in the past.
You can program the SG II to see the AWD engage.
#29
05-21-2010, 09:48 AM
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Re: Bad PTU-Am I the first?
On a tractive surface unless the front and rear tires have close to equal wear and are equally inflated you will ALWAYS have some minor level of driveline windup and/or tire scrubbing with all four wheels being driven. Even worse when turning. Anytime you incur driveline windup and/or tire scrubbing the PTO will be under stress.
So this F/awd system is much more about improving the safety of what would otherwise be a PATENTLY unsafe vehicle vs adding wintertime adverse roadbed traction capability.
In point of fact if the TC/VSC should detect front wheelspin/slip the system literally goes into "limp home" mode temporarily. FULL dethrottling, drive crippling mode. Disable TC to get around this design flaw and you're left, in the WORSE of conditions, with a simple, HAZARDOUS FWD vehicle
Last edited by wwest; 05-21-2010 at 09:57 AM.
#30
05-21-2010, 11:29 AM
Re: Bad PTU-Am I the first?
Yes, as I understand it you get a relatively HIGH level of torque coupling to the rear with straight-line acceleration but a somewhat (substantially..??) lower torque coupling level in an accelerating turn. The tighter the turn and/or the higher the acceleration rate the lower the rear drive coupling coefficient should (will..?) be.
Anyway, driving straight, from a dead stop, pedal to the floor, I've never seen more than around 35% which can also be seen on turns too.
