Ever since General Motors acquired a controlling interest in Group Lotus, its divisions experimented with active suspension. GMC applied this technology to a four-wheel-drive pickup truck, a special Sierra 400 built for the 1988 Chicago Auto Show.
Just as in the revolutionary Lotus 88 racing car, the Sierra featured a computer-controlled hydraulic actuator at each wheel in place of a conventional shock absorber. Displacement, load, and acceleration sensors fed input to a large computer, which in turn actuated the suspension through a high-volume hydraulic pump. In prototype form, the active-ride system added 400 pounds to the truck’s weight.
The active ride (hence, A/R) suspension promoted crisper transitions on the highway. Off-road, it smothered washboard surfaces, prevented bottoming, and did a good job of isolating the cab from the turmoil at ground level. The only drawback was the oversized hydraulic pump absorbed 40 bhp of the engine’s output.
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