AWD question
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Joined: Jan 2000
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From: Along Lake Erie
I'll defer to the service manual:
Basically it's rear wheel drive until it slips. At that point, the system momentarily engages the transfer case until all four wheels are turning the same speed, and then it releases.
Make sense?
All Wheel Drive (AWD)
The all wheel drive (AWD) consists of the following components:
PCM/4X4 control module
Integrated wheel end (IWE) solenoid
IWEs
The Borg-Warner one-speed torque-on-demand (TOD) transfer case is a 3-piece aluminium design. The transfer case is equipped with an internal electromagnetic clutch. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions, the unit is in AWD, but when desired, the operator may shift into four wheel drive high (4H). The transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.
The all wheel drive (AWD) consists of the following components:
PCM/4X4 control module
Integrated wheel end (IWE) solenoid
IWEs
The Borg-Warner one-speed torque-on-demand (TOD) transfer case is a 3-piece aluminium design. The transfer case is equipped with an internal electromagnetic clutch. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions, the unit is in AWD, but when desired, the operator may shift into four wheel drive high (4H). The transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the rear output shaft.
Make sense?
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Member
Joined: Feb 2006
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From: Northwest Washington
Thank you for the detailed information. The dealer could not really explain to me how the system worked in detail. FYI the 08' Limited (what I own) has the AWD option for a tranfer case. Mine has AWD and limited slip 3.73 rear end. 
Senior Member
Joined: Jan 2000
Posts: 3,205
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From: Along Lake Erie
Originally Posted by Foozeball67
Thank you for the detailed information. The dealer could not really explain to me how the system worked in detail. FYI the 08' Limited (what I own) has the AWD option for a tranfer case. Mine has AWD and limited slip 3.73 rear end.
It's splitting hairs, I know, but functionally they're not the same system.
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Originally Posted by GIJoeCam
For the record, it's not all wheel drive. In an AWD vehicle, power is sent to all four wheels, generally via a viscous coupling or center differential setup. The system on the trucks sends all the power to the rear wheels until they slip. That's considered automatic 4 wheel drive, not AWD.
It's splitting hairs, I know, but functionally they're not the same system.
It's splitting hairs, I know, but functionally they're not the same system.
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Joined: May 2007
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From: Concord NC
Originally Posted by GIJoeCam
For the record, it's not all wheel drive. In an AWD vehicle, power is sent to all four wheels, generally via a viscous coupling or center differential setup. The system on the trucks sends all the power to the rear wheels until they slip. That's considered automatic 4 wheel drive, not AWD.
It's splitting hairs, I know, but functionally they're not the same system.
It's splitting hairs, I know, but functionally they're not the same system.
Rats!
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Joined: Sep 2006
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From: North Pole, Alaska
I think all AWD does is get you stuck in mud and snow. Girlfriend had a Merc Mountanier that had AWD, in the snow first the rear wheels would break loose and then the front wheels after that the truck has 4 nice little holes dug and it was stuck.
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Joined: Jan 2000
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From: Along Lake Erie
Originally Posted by LastSplash
I think all AWD does is get you stuck in mud and snow. Girlfriend had a Merc Mountanier that had AWD, in the snow first the rear wheels would break loose and then the front wheels after that the truck has 4 nice little holes dug and it was stuck.
If you're in the snow like that, the key is to recognize the need to lock the transfer case in 4high, not run around in 4auto. The 95 and 96 lacked the option of locking in 4high, but there's an easy way around that with a piece of wire, $5 switch, and a couple of hours.
-Joe
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Joined: Jan 2000
Posts: 3,205
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From: Along Lake Erie
Freestyle/Taurus X uses a different setup... From the description of the system in the service manual, I get the impression that it uses something akin to an electronically controlled viscous coupling... if such a thing exists. I suppose a VC with electro-rheostatic fluids could be at play (fluids that change viscosity with electric charge applied), but the manual doesn't explain it.
Interesting... I'm thoroughly intrigued... I need to shoot some e-mails.
Power Transfer Unit (PTU) Printable View (150 KB)
Torque from the engine goes through the transaxle to the power transfer unit (PTU). Torque is transferred from the driveshaft to the rear axle, which drives the rear halfshafts.
The vehicle is equipped with an intelligent all wheel drive (AWD) system that is always active and requires no driver input. The AWD system combines transparent all-surface operation, and is capable of handling all road conditions, including street and highway driving as well as winter driving. The AWD system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and rear wheels. During normal operation, most of the torque is sent to the front wheels. If wheel slip between the front and rear wheels is detected, or if the vehicle is under heavy acceleration (HIGH THROTTLE position), the AWD system increases torque to the rear wheels to prevent or control wheel slip.
Serviceable components of the PTU are limited to the output shaft seal and flange, intermediate shaft seal and deflector and the input shaft seal. If any of the internal geared components, bearings or shafts are worn or damaged, a new PTU must be installed. The PTU is sealed from the transaxle and has its own oil sump
Torque from the engine goes through the transaxle to the power transfer unit (PTU). Torque is transferred from the driveshaft to the rear axle, which drives the rear halfshafts.
The vehicle is equipped with an intelligent all wheel drive (AWD) system that is always active and requires no driver input. The AWD system combines transparent all-surface operation, and is capable of handling all road conditions, including street and highway driving as well as winter driving. The AWD system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and rear wheels. During normal operation, most of the torque is sent to the front wheels. If wheel slip between the front and rear wheels is detected, or if the vehicle is under heavy acceleration (HIGH THROTTLE position), the AWD system increases torque to the rear wheels to prevent or control wheel slip.
Serviceable components of the PTU are limited to the output shaft seal and flange, intermediate shaft seal and deflector and the input shaft seal. If any of the internal geared components, bearings or shafts are worn or damaged, a new PTU must be installed. The PTU is sealed from the transaxle and has its own oil sump
Principles of Operation
Differential Electronic Module (DEM) and Active On-Demand Coupling
The main role of the active on-demand coupling and the differential electronic module (DEM) is to regulate the all wheel drive (AWD) function by distributing torque between the front and rear axles. The system consists of a coupling that combines mechanical, hydraulic and electronic sections. The coupling unit is attached to the rear axle, between the differential gear and the driveshaft. The mechanical and hydraulic sections are driven by the driveshaft. Active on-demand coupling (AOC) has the following characteristics:
Permanent AWD with electronic control of torque transfer front to rear
4X4 control module integrated into the DEM
Similar to four wheel drive (4WD) operation
No driveline wind-up during slow speed maneuvers or parking
The system is not sensitive to size differences between the 4 road tires (when driving with a spare wheel, for example). The system is not sensitive to being towed with one axle raised.
Differential Electronic Module (DEM) and Active On-Demand Coupling
The main role of the active on-demand coupling and the differential electronic module (DEM) is to regulate the all wheel drive (AWD) function by distributing torque between the front and rear axles. The system consists of a coupling that combines mechanical, hydraulic and electronic sections. The coupling unit is attached to the rear axle, between the differential gear and the driveshaft. The mechanical and hydraulic sections are driven by the driveshaft. Active on-demand coupling (AOC) has the following characteristics:
Permanent AWD with electronic control of torque transfer front to rear
4X4 control module integrated into the DEM
Similar to four wheel drive (4WD) operation
No driveline wind-up during slow speed maneuvers or parking
The system is not sensitive to size differences between the 4 road tires (when driving with a spare wheel, for example). The system is not sensitive to being towed with one axle raised.
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Joined: Jan 2008
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good thread.. i bought an 08 harley f150 and was always wondering how the AWD worked
i was in the snow today... and i noticed that my back end went out for a split second before it regained grip... i just put it in 4H and i was pretty good after that
i was in the snow today... and i noticed that my back end went out for a split second before it regained grip... i just put it in 4H and i was pretty good after that
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Joined: Jan 2007
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So is the switch on the dash in the 06+ harleys for AWD-4HI switching from an automatically engaging and disengaging as needed 4HI and a full-time 4HI? And the only real difference between this and the normal 4x4 ford is that there is no 4LO available?