2002 GMC Sierra Denali with Quadrasteer

GMC Unveils Three Technologies That Will Change Your Pickup Truck Forever

By: Michael Levine and John Gillies Last Edited: 07-08-01 12:00
PickupTruck.com, © 2001

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Who says you can't drive concept vehicles? Well, you still might not find GMC's Terradyne parked in your driveway anytime soon but in the near future three cutting-edge, concept-worthy technologies will change the way you drive and use your pickup.

We spent two days with GMC in La Jolla, California getting familiar with four-wheel steering and two new powertrains featuring automatic cylinder shutoff and hybrid gasoline-electric propulsion.


Back in 1988 Honda became the first auto maker to introduce four-wheel steering, in its compact Prelude sedan. About the same time GM was showcasing a much more advanced version of four wheel steering in its Blazer XT-1 concept vehicle. For whatever reason the feature never took off, probably because the Prelude's purely mechanical setup didn't provide much benefit in the already nimble car and the XT-1's system was as complex and expensive as a NASA X-plane.

Enter the 2002 GMC Sierra Denali, the successor to the 2001 Sierra C3. The Sierra Denali makes an already outstanding truck even better with the addition of Quadrasteer four-wheel steering, aka QS4.

Quadrasteer electronically controls the rear wheels at different speeds and under various load bearing conditions to create an amazing amount of agility and maneuverability - especially when towing or parking. The rear wheels turn in proportion to the front up to a maximum 12-degree angle depending on vehicle speed and driving
mode. 12-degrees may not seem like a lot but consider the following: at 37.4 feet the Sierra Denali's turning radius in four-wheel steer mode is only three inches greater than that of a three door Saturn coupe! That's almost 10 feet smaller than the 2001 Sierra C3 was capable of performing! Quadrasteer on the 2002 Sierra Denali is a game-changer.

The 2002 Sierra Denali's turning radius is almost 10 feet smaller than the 2001 Sierra C3.

Quadrasteer steer-by-wire rear axle is controlled by two sophisticated microprocessors. At low speeds the rear wheels turn in the opposite, or negative, direction of the front wheels up to a transition zone of around 40 to 45 mph where the rear wheels track neutrally. At speeds over 45 mph the rear wheels turn in concert, or positively, with the front. If at any time the two microprocessors 'disagree' over the steering information they have received QS4 automatically shuts down and reverts back to traditional two-wheel steering.

Located on the dash of the Sierra Denali is a push button Quadrasteer control panel similar to the four-wheel drive control panel found in many trucks today. The driver pushes the button to change steering modes from two-wheel steer (2WS) to four-wheel steer (4WS) to four-wheel steer tow (4WS TOW). In 4WS mode the rear wheels turn up to the maximum allowable amount below 40-45 mph. The wheels transition and turn in the same direction as the front above this speed. When towing, Denali drivers can select 4WS TOW. 4WS TOW reduces the amount of rear wheel steer at slower speeds, when the wheels are turning in opposite directions, but increases it at higher speeds when the wheels turn in the same direction.

With Quadrasteer, drivers can select 2 Wheel Steer, 4 Wheel Steer or 4 Wheel Steer Tow Modes using a push button control panel on the dashboard.

Created in an exclusive partnership with Tier 1 supplier Delphi automotive, GMC won't comment on how long this arrangement will last. Dana Corporation provides the Sierra Denali's axle and Delphi completes the final assembly, adding the electronics and delivering the final unit to GM's Oshwa, Ontario plant where the Denali is produced.

The Quadrasteer system adds a weight penalty of about 285 pounds to the truck but gives back this amount and more in additional towing and hauling capabilities over the C3. The rear axle's weight rating increases by 250 pounds to 4000 pounds and maximum GCWR (gross combined weight rating) climbs from 14000 to 16000 pounds. Trailering capacity has increased from 8700 pounds to 10000 pounds. The wider rear axle also provides more stability when towing.

Sam Mancuso, the Sierra Brand Manager, proudly proclaims, "The Sierra Denali is the most capable ½-ton pickup truck available in its class. There is nothing else like it from Ford, Dodge or Toyota."

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