474:. The viscous coupling replaced the typical center differential used in four-wheel drive applications. The system worked normally in front wheel drive but in addition to the front wheels being driven, a shaft is powered that runs to the viscous coupling in the rear. If the front wheels slip, the viscous coupling progressively releases torque to the rear wheels. Additionally, the ControlTrac II system provided a mechanical lock of four-wheel drive though there was no low range provided by the system.
377:. The computer control system needs the front drive shaft to turn, so that it can monitor and compare the rotational speed of both the front and rear drive shafts. If the rear drive shaft starts to turn faster than the front, the system interprets that (along with input from other sensors) as traction loss. When traction loss is detected, torque is sent forward to the front differential in 10 percent increments, via the center multi-disc clutch. As it does so,
369:, full-time four-wheel drive capability on pavement as needed. In Auto mode, the engine's torque is normally routed to the rear drive wheels. A misconception about the system is that it continuously shifts into and out of four-wheel drive as needed. This is not true, for when Auto mode is selected, the front axle hubs are permanently engaged, locking them to the front axle shafts, front differential, and front
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Four High and Four Low modes were also featured on both
Explorer and Expedition. Four High mode tells the intelligent locking multi-disc differential to lock, providing a permanently locked 50:50 torque distribution. The front and rear drive shafts are fully locked, forcing them to rotate at the same
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Predominantly, Explorer was not equipped with Two High mode except in the 1995-1996 model years. In model years 1998-up no Two High was available. Only Auto, Four High and Four Low modes were offered. Two High mode was unique to the
Expedition, though it was discontinued between the 1999–2002 model
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would review input from sensors every 20 milliseconds and decide if the front axle needed more torque. Using this technique, the unit's computer watched for drive wheel slip. If it sensed as little as half an rpm difference between the front and rear axles, it sent a power signal to the multi-disc
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However, heat proved to be a persistent issue. Excessive heat buildup would burn out the new clutch material. To solve the problem, engineers studied the clutch's torque capacity. It was determined that excessive heat buildup was caused by inadequate clutch torque capacity. Engineers increased the
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with the intelligent multi-disc clutches being called upon for almost continuous delivery of torque. At first, the environment quickly burned out the clutches. But as engineers gained knowledge, the clutches improved. Eventually, the engineers were able to improve the clutch packs enough that the
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ControlTrac II has since been replaced by the automatic
Intelligent four-wheel drive system, a similar system with the viscous coupling replaced by a computer controlled clutch. The Intelligent 4WD system functionally acts similar to the ControlTrac II system, with the front wheels being driven
414:. Reduction gearing is utilized to reduce the vehicle's speed to a manageable crawl, and to increase (multiply) the supplied torque coming from the engine. Thus the drive wheels have ample torque to move the vehicle at low speeds. It is also used to control downward speeds while descending steep
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allowed the multi-disc clutch pack's friction and clutch discs to slip as needed, simulating a planetary or bevel geared center differential, making a geared differential redundant. Thus, the geared differential was abandoned and therefore never included on the final production version of the
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ControlTrac has different drive modes as well as different operational behavior for those drive modes depending on which vehicle it is used in. For example, the Ford
Expedition used a new auto lock feature in Auto mode. Auto mode with auto lock was not available on the Explorer at that time.
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traction loss before it happened, so that torque can be transferred before it was needed. This improvement meant the system could operate more like other "always-on" full-time four-wheel drive systems as it no longer had to "wait" for traction loss to take action. Another improvement was
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amplifiers and large control modules consumed the entire back end of a station wagon. Input data came from variable reluctance sensors installed at the front drive shaft, rear drive shaft, throttle, brakes, and steering. The goal was to control clutch actuation by controlling current.
258:, they could control the variable electromagnetic multi-disc clutch to a point where it would allow the front and rear drive shafts to turn at different rotational speeds on its own, without the aid of a planetary or bevel geared center differential. In Auto mode the new software
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differentials. By ABS brake locking the front and rear differentials, up to 100 percent of torque can be sent to any one drive wheel, allowing the vehicle to keep moving, even with two of its drive wheels (one front, one rear) completely off the ground.
441:. The combination of these two systems is innovative due to a vehicle equipped as such, can continue to move forward with only one wheel having traction. AdvanceTrac's four-wheel electronic traction control system uses the vehicle's four-wheel four-
397:" capability in Auto mode. ControlTrac's intelligent multi-disc differential could now send all 100 percent of the engine’s torque forward, biasing it to the front differential if severe traction loss was anticipated, predicted, or detected.
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clutch. The clutch engaged, diverting torque to the front axle in 10 percent increments, until it alleviated the drive wheel slip. As a result, the system could control runaway drive wheel speed in as little as a third of a wheel revolution.
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The geared center differential would be used to allow the front and rear drive shafts to turn at different rotational speeds so as to eliminate any "drivetrain binding" or "torque windup" while the system was being used on
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that would disconnect the front axle, front differential, and front drive shaft when not needed for quieter, more fuel-efficient operation on pavement. Ford claimed that the improved Two High mode could help increase
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years. Two High mode was reintroduced on the redesigned second generation
Expedition (U222) for the 2003 model year and featured a new full front axle disconnect system with vacuum operated front
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We asked ourselves: Why do we need a differential? There was all of that iron, all that weight, all that cost. And here, we saw that we could control the clutch pack very precisely without it.
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clutch material that exhibited an operating condition commonly known as "stick slip." The slippage had inspired engineers to replace it with a paper-based material mounted atop
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predominately with torque being sent to the rear wheels only as conditions dictate. The
Intelligent 4WD system also lacks the mechanical lock provided by ControlTrac II.
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Both Four High mode and Four Low mode cannot be used on pavement as "driveline binding" and "torque windup" can occur, causing damage to the four-wheel-drive system.
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control software allows the center multi-disc clutch to behave like a geared center differential, such that "driveline binding" and "torque windup" do not occur.
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speed regardless of tractive conditions. Four Low mode also tells the intelligent locking multi-disc differential to lock, however it instructs the BorgWarner
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The idea for an electronically controlled four-wheel drive system emerged at BorgWarner in 1985. BorgWarner's original design called for using both a
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The design team gained confidence in their concept in 1989, when they made a breakthrough in the multi-disc clutch's control system. Development of
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2011 Ford
Explorer (U502) replaced automatic ControlTrac four-wheel drive with automatic Intelligent four-wheel drive and Terrain Management.
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In the early 2000s, ControlTrac was updated and introduced in 2002 with more advanced software programming, building on the system's
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division in the mid 1980s. BorgWarner calls the system Torque-On-Demand (TOD). ControlTrac was the first automatic system to use
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up to half-a-mile per gallon of gasoline. In Two High mode, torque is routed to the rear drive wheels only, imitating
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controlled electromagnetic multi-disc (also called multi-plate) clutch pack and a planetary or bevel geared center
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geared center differential. Instead of a planetary or bevel geared center differential, the system uses a variable
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smoothed its operation. Using it, the multi-disc clutch made smaller adjustments, but did it more frequently. The
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Within a year, the controller had become larger and more complex. A breadboard electronic version complete with
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test vehicles could be virtually destroyed from hard off-road use, but the clutch packs would still look good.
93:. A heavy-duty version of ControlTrac was introduced in 1996 for the 1997 model year on the first generation
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when needed and would also lockup providing a permanently locked front 50:50 rear torque distribution.
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302:. The paper offered a better coefficient of friction and solved the slippage problem. BorgWarner's
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system's capacity and equipped a fleet of test vehicles, which they took to the
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ControlTrac four-wheel drive
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ControlTrac II was a Ford four-wheel drive system based on a
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Early in the development, BorgWarner had employed a sintered
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ControlTrac made its debut on January 12, 1995, for the 1995
45:. The four-wheel drive system was designed and developed at
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back-to-front and front-to-back between the front and rear
596:"Control Trac® delivers automatic torque split, low-range"
549:"New Ford Expedition Features Borg-Warner Transfer Case"
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37:of a selectable automatic full-time
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740:Four-wheel-drive system tradenames
457:locking" either the front or rear
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97:full-size sport utility vehicle.
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668:"2003 Ford Expedition Overview"
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410:to select low range off-road
401:Four High and Four Low modes
435:electronic stability control
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725:Article about ControlTrac
263:four-wheel drive system.
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85:on the second generation
551:. www.thefreelibrary.com
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33:four-wheel drive is the
386:artificial intelligence
71:multi-disc differential
304:automatic transmission
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207:Design and development
146:Ford Expedition EL/Max
698:. www.ford-trucks.com
670:. www.ford-trucks.com
619:. www.ford-trucks.com
598:. www.ford-trucks.com
570:"BorgWarner Products"
472:viscous coupling unit
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91:sport utility vehicle
572:. www.borgwarner.com
525:. www.designnews.com
272:Ronald A. Schoenbach
256:software programming
219:together. The first
184:Lincoln Navigator L
51:TorqTransfer Systems
750:Ford vehicle design
279:closed-loop control
453:via aggressively "
451:differential locks
43:Ford Motor Company
41:system offered by
638:"Intelligent 4WD"
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317:in southern
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217:differential
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163:MY1998–2006
124:MY1995–2010
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77:Availability
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429:AdvanceTrac
420:crawl ratio
379:intelligent
371:drive shaft
111:Model Year
67:intelligent
31:ControlTrac
745:BorgWarner
734:Categories
702:2012-09-10
674:2012-09-10
644:2012-09-10
623:2012-09-10
602:2012-09-10
576:2012-09-10
555:2012-09-11
529:2012-09-10
482:References
459:drive axle
319:California
260:algorithms
166:two-speed
153:two-speed
140:two-speed
127:two-speed
83:model year
49:under its
47:BorgWarner
35:brand name
27:Brand name
416:gradients
361:Auto mode
221:prototype
89:mid-size
59:planetary
270:—
233:pavement
225:rheostat
213:software
108:Vehicle
55:software
390:predict
367:weather
443:sensor
315:desert
296:bronze
248:sensor
237:torque
455:brake
375:speed
330:Modes
300:metal
63:bevel
323:sand
199:The
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