[4] ControlTrac made its debut on January 12, 1995, for the 1995 model year on the second generation Ford Explorer mid-size sport utility vehicle.
[1] A heavy-duty version of ControlTrac was introduced in 1996 for the 1997 model year on the first generation Ford Expedition full-size sport utility vehicle.
[1] 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 pavement.
A breadboard electronic version complete with sensor amplifiers and large control modules consumed the entire back end of a station wagon.
[1] However, as the development process continued, engineers at BorgWarner discovered that, with clever software programming, 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.
The clutch engaged, diverting torque to the front axle in 10 percent increments, until it alleviated the drive wheel slip.
[1] Early in the development, BorgWarner had employed a sintered bronze clutch material that exhibited an operating condition commonly known as "stick slip."
Engineers increased the system's capacity and equipped a fleet of test vehicles, which they took to the Anza-Borrego desert in southern California.
They made a total of 11 trips, subjecting the prototypes to heat, mountain driving, and deep sand with the intelligent multi-disc clutches being called upon for almost continuous delivery of torque.
[7] Ford claimed that the improved Two High mode could help increase fuel economy up to half-a-mile per gallon of gasoline.
Auto mode was featured on both Explorer and Expedition and allows for all-weather, full-time four-wheel drive capability on pavement as needed.
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.
In the early 2000s, ControlTrac was updated and introduced in 2002 with more advanced software programming, building on the system's artificial intelligence.
[4] 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.
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.
[7] AdvanceTrac's four-wheel electronic traction control system uses the vehicle's four-wheel four-sensor four-channel anti-lock braking system (ABS) and is programmed with additional anti-slip logic to simulate differential locks via aggressively "brake locking" either the front or rear drive axle differentials.