Pro Pickup

The Big Book of Buyer's Guide 2013

Propickup Digital Magazine

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LOCKERS & LIMITED SLIPS TRACTION DIFFERENTIA L A lmost every new full-size pickup comes equipped with an electronic traction control that is part of the vehicle's ABS and stability control system. The same network of sensors, computers, valves and solenoids that keep the brakes from locking up under panic stops can also detect if a drive wheel is spinning faster than the other wheels, which indicates a loss of traction. The system quickly reacts by applying the brake on the spinning wheel, which transfers torque across the axle to the tire with greater traction when in two-wheel-drive or, if needed, to the opposite axle when in fourwheel-drive. The computer can also reduce engine power until all the drive wheels share the workload evenly. Electronic traction control is effective in the majority of routine driving situations, especially on ice or snow-packed roads. The sophisticated programming that makes split-second adjustments to control the tires is well beyond the driving capability of most drivers. Besides helping achieve maximum grip for braking and acceleration, brake controls can also help the driver maintain the desired course in a turn (electronic stability control) and reduce trailer yaw (trailer sway control). Despite all their wonderful attributes in day-to-day driving, electronic traction controls have shortcomings in more severe applications such as off-highway use. So most automakers still offer optional mechanical traction aids, such as a limited-slip differential (LSD) or a locking differential. The Toyota Tundra is the only full-size pickup that does not offer a mechanical LSD or locker, but it has advanced programming options in its electronic traction controls to help drivers get out of difficult situations. Besides increased brake-pad wear, the biggest drawback to electronic traction controls is that they may cut engine power and work to eliminate all wheelspin. For situations such as climbing a steep hill on loose dirt or slogging through deep sand, the driver needs power and some wheelspin to maintain momentum or "dig out." That's where the mechanical traction aids provide the most effective assistance. The other big drawback is driver frustration when the computer intrudes during aggressive off-roading, like when you lay into the throttle in sand or heavy mud to get the tires to clean and keep forward momentum. Pickup manufacturers give drivers the option to turn off traction and stability controls, and some vehicles do it automatically when in certain 4WD modes. But even that might not be enough to keep your truck from getting stuck. TRACTION UPGRADES The work and recreational needs of many truck owners may require upgrading of a stock vehicle's drivetrain with some type of mechanical traction assistance. The actual workload and owner's pocketbook will determine the best option. Limited-slip differentials have been around since the '50s. They may use internal friction clutches – either flat or cone style – or a unique worm-gear arrangement to limit torque to the spinning 74 PROPICKUP Big Book 2013 ProPickup_2013BB_Lockers Limited Slips.indd 74 8/6/13 10:17 AM

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