The 1999 GMC Sierra is built on the stiffest and lightest truck frame that GMC has ever designed. The front frame rails are hydroformed, using high-pressure hydraulic presses and fixtures to shape steel tubing. Tubular crossmembers and roll-formed mid-rails are used to increase rigidity further. From the strong foundation of the new frame and crossmembers, the engineers get much better handling and ride quality, with greatly improved structural strength in collision situations.There are three new V8 engines, in 4.8-, 5.3- and 6.0-liter displacements. All three are based on the small-block V-8 design that was introduced on the Corvette two years ago and used in the Camaro and Firebird last year. A 4.3-liter V6 is the base engine and it, too, comes into 1999 with a number of improvements. And then there's the 6.5-liter turbo diesel monster engine for the 2500 series only. A 5-speed manual gearbox is standard in the base truck, but the 4L60 and 4L65 4-speed automatics, with a delayed-upshift feature for towing will be chosen by 95 percent of buyers. The Sierra has an aluminum-intensive short- and long-arm front suspension, with coil springs on two-wheel-drive models and torsion bars on four-wheel-drive models. Heavy-duty disc brakes come on all four corners as standard and ABS is standard on all models.
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