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Friday, March 12th, 2010

Years ago when somone used the term traction aids they were referring to weights and pulleys to put tension on a displaced bone or joint. The reference still exists in medical vernacular. Today, traction aid is a buzz term for any of the new technologies for cars and trucks that help guide them along their path safely with driver control.traction control

Most of the new systems are seamless and mostly automatic to offer the driver options for dealing with just about any low-traction situation. As with many new technologies, there can be confusion as to what they do and when they should be employed.


Maximum traction is not always the desired result. There is a problem designing a system for both optimum control and maximum traction. The reason is that tires are required to generate both traction forces and cornering forces. Although they can do both at the same time, they cannot generate 100 percent of both at the same time. If a tire is asked to maximize traction, its cornering capability will be significantly reduced, and visa versa. This is the main reason Auto LSD works separately from TRAC. TRAC is geared more toward control, while Auto LSD is all about traction. So what are the differences?

VSC is the default mode on many Toyota vehicles and incorporates TRAC. It is referred to as VSC+TRAC. These two systems are functional in 2WD  vehicles, or 4WD vehicles in 2WD mode.

TRAC – Helps improve traction by limiting rear wheel-spin with throttle reduction and/or by applying the rear brakes. It is programmed to help improve traction and limit the chance of losing control of the vehicle due to too much rear wheel-spin say as you drive along a wet road.

A-TRAC– Is TRAC for 4WD vehicles. When in 4WD, A-TRAC monitors wheel-spin on each axle. It uses the brakes to limit wheel-spin on opposing tires, thus transferring torque from the spinning wheel to the non-spinning wheel, helping to improve traction on that axle.

VSC– Helps control the vehicle during cornering and has virtually nothing to do with traction. It is designed to counter-steer the vehicle in case of loss of control in a cornering situation by applying individual brakes. This helps the vehicle stay along its intended path. The steering effect is much like steering a wheelchair by grabbing /braking one of the wheels.

VSC OFF- Helps give the driver control over wheel-spin for conditions that require more slip, such as deep snow with tire chains. It also allows “rocking” of the vehicle if stuck. This is accomplishing by holding in the VSC Off button for more than three seconds. Both the VSC Off and slip indicator light will illuminate. VSC can be turned on again by simply pushing the VSC Off button.

AUTO LSD Designed for maximum longitudinal tire traction, is only functional in 2WD vehicles or 4WD vehicles in 2WD mode. The electronic programming of Auto LSD uses the brakes to slow a spinning rear tire which redirects the power to the tire with grip, just like TRAC, but without power reduction. Auto LSD need only be used when the VSC-TRAC system is not sufficient for conditions such as pulling a boat up a wet ramp.

The system can be engaged any time by tapping the “VSC OFF” switch. An “Auto LSD” light appears in the gauge cluster. Auto LSD only functions below about 30 mph; above that, TRAC takes over regardless of the indicator lights. To turn Auto LSD off, simply tap the switch again.

Whether the goal is improving control or traction, these systems do an outstanding job and are standard on many Toyota vehicles, Tundra and Tacoma.