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Discussion Starter · #1 ·
I have a 2008 XLT V6 (not flex fuel if that matters) with nearly 190k on it. The AWD stop working when the car was my parents, and according to them there was no signs, noises, lights, or any warning before it went. It wasnt gradual, just did not work one day. I havent got any codes for it, the awd light still comes on at startup, and when i put the vehicle on a lift only the front driver wheel spun and the driveshaft did not move at all. As far as i know, its either a speed sensor, control module, or transfer case issue, but I have no clue how to continue diagnosing at this point. Has anyone had similar problems, or any information on the testing of these component or how they should normally operate? Its hard to find operation and specs on them. Id just like to figure out what the issue is myself so i dont have to pay a ridiculous amount to go to a dealer and get it diagnosed, since I can likely fix it myself anyway.
 

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I have a 2008 XLT V6 (not flex fuel if that matters) with nearly 190k on it. The AWD stop working when the car was my parents, and according to them there was no signs, noises, lights, or any warning before it went. It wasnt gradual, just did not work one day. I havent got any codes for it, the awd light still comes on at startup, and when i put the vehicle on a lift only the front driver wheel spun and the driveshaft did not move at all. As far as i know, its either a speed sensor, control module, or transfer case issue, but I have no clue how to continue diagnosing at this point. Has anyone had similar problems, or any information on the testing of these component or how they should normally operate? Its hard to find operation and specs on them. Id just like to figure out what the issue is myself so i dont have to pay a ridiculous amount to go to a dealer and get it diagnosed, since I can likely fix it myself anyway.
Check fuses/relays first, if you have not already
Is it a paperweight, or does the car drive at all?
 

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The PTU/Transfer case has no logic, it always just transfers power to the rear. The rear end contains the "clutch" used to regulate how much is transferred.

What indication do you have no AWD? If the passenger side wheel didn't move the opposite direction if you turned the other one, or if you powered it with the engine, the passenger side should have a jack shaft to the PTU then the CV axle to the front wheel.

Sounds mechanical to me, if passenger front wheel is also disconnected could be the output/jackshaft from transmission, if it is connected sounds like the PTU is toast (if the output shaft of it doesn't turn the driveshaft).
 

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Discussion Starter · #4 ·
Check fuses/relays first, if you have not already
Is it a paperweight, or does the car drive at all?
The fuses should be good, my dad and uncle both checked them and they're an electrician and a mechanic so I'd hope they know. The car works fine otherwise, I drive it everyday, traction control and abs work great. I did replace the 2-4 band on the transmission when it went and it shudders/jerks a little but I attribute that to age and the shitty trans. Externally the transfer case seems fine as well.
 

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Impossible for this to be electrical.

If the driveshaft doesn't rotate, the PTU isn't transferring power.

That means that either the PTU failed internally or the shaft that goes into the transmission or the part in the transmission that the shaft engages has sheared.
 

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The transfer case doesn't have a module, the control module is for the active coupler in front of the rear diff.
 

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Discussion Starter · #8 ·
I have not done all the pinpoint tests but I used a good autel scan tablet and believe I ran both koeo any koer tests without and issues detected. It was a while ago at this point and I don't fully remember, but I know I never had any issues detected or fault codes for anything drivetrain related
 

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Well-intended but incorrect information aside, as I and several other guys pointed out, this isn't an electrical or electronic problem. If the driveshaft isn't turning in conjunction with the RH halfshaft or that halfshaft isn't turning when it's supposed to, something is mechanically busted.

Don't forget that this is an open differential... Only one of the two front halfshafts are going to have power at a time.You may have to stall the LF wheel in order to properly assess the operation of the drivetrain.
 

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Discussion Starter · #10 ·
So it should be normal for the halfshaft not to be driven when in drive on the lift? Would I have to look on the ground while it's being driven to actually see what moves and what doesn't? Or could I make the driveshaft, drive it, and see if the mark changes?
 

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Don't forget that this is an open differential... Only one of the two front halfshafts are going to have power at a time.You may have to stall the LF wheel in order to properly assess the operation of the drivetrain.
An open differential allows the wheels to turn at different rates in a turn. By design, torque will go to the wheel with the least resistance. On a lift just one may turn unless the other has resistance.

Sent from my moto g power using Tapatalk
 

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You had it on a lift, all 4 wheels off the ground, and only the front drivers wheel moved when you had it in gear and let off the brakes? I am not sure that is a bad thing, as mentioned with the open diff. If you have all four wheels off the ground, the vehicle in neutral, and you turn the passenger wheel, you should get the PTU output to turn the driveshaft to the rear, and the drivers wheel should turn the opposite direction.

What indications do you have that AWD is not working? Do you get codes? Have you noticed that power isn't going to the rear because you have been stuck or on slippery surface and had problems?

My 2012 Fusion Sport AWD with basically the same setup, nearly every take off from a stop AWD is 50/50 split, and I can tell just because it doesn't spin a tire. I have data logged the wheel speeds, the AWD torque split, and it is pretty easy to tell that way also. I have also driven it on ice and in slush and been able to get out of some pretty bad situations (well, not middle of the country off roading, but snow plow leaving a 3 foot tall berm next to me parked on the street).
 

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As others have said, something broke, mechanically..

It's either the PTU, a stripped spline, or the internal cage inside the diff/transaxle. Any diagnosis is going to require a teardown.

Mine went out the same way. According to the SM, the system will provide 100% of the torque to the rear end if the front end is slipping. The clutching is done in the rear diff assy, not the PTU (which is only a geared box), so if the driveshaft is turning with the truck off the ground, the rear isn't transferring the torque. If the driveshaft doesn't turn, it's busted in the front end.

John
 

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Discussion Starter · #14 ·
Thanks for the info, after some more research and talking with some technicians and looking on identifix I arrived at the same spot. Now I just have to figure out when I can tear it apart.
 

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How did your parents recognize the AWD failed suddenly? Did they get stuck, unable to move, where they normally would not? I have a 05 Escape hybrid with AWD. I'll check mine tomorrow to see if the rear driveshaft turns on the lift. Unless the AWD light was on, I wouldn't know if the AWD had failed. Have you tried some real world testing, like a sandy area, and have a friend watch the tires for spin, or lack of?

There is an AWD module monitoring the electrical side of the system, but I don't know if it would detect a mechanical failure of the system.
 

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Discussion Starter · #16 ·
I believe they went to use it after a snowstorm a few years ago and the car suddenly had very little grip and slipped a lot when before it had been decent in the snow. I've watched it slip trying to get into a driveway with a maybe 5% grade with minimal snow, and now that it's mine it even spins the front tires on mildy wet roads and the rear wheels do nothing. I did see on identifix the car should be in drive and I did it in neutral, I'm not sure if this would effect the driveshaft being engaged.
 

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I hosted the vehicle this morning. Again, 05 Escape hybrid AWD. This should be the same as a 2008. Engine running and in drive, all four wheels rotated forward. The both driver's side rotated at the correct speed and the passenger side both rotated at a 1/3 speed.

I tried ProjectSH099's test and yes the drive shaft did rotate.
 
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