Both GMC and Chevrolet redesigned their full-size pickups for 1999. Sierras came in half-ton 1500 (listed here) and light-duty 3/4-ton 2500 form. GMC dealers also kept selling pickups from the old design, right alongside the new ones. GMC models now had their own front-end sheetmetal. Wheelbases increased by 1.5 inches for regular-cab models, and 2 inches for extended-cabs. Body lengths grew by about 9 inches. A right-side third door, which opened only after the front door was unlatched, was standard on extended-cab pickups. Both body styles came with a 6.5- or 8.1-foot Wideside cargo bed, or a 6.5-foot flare-fender Sportside box. Antilock braking again was standard, but 4-wheel disc brakes were new. Also new was an adjustable ride control option that allowed the driver to switch between two levels of shock-absorber firmness. A 4.3-liter V6 again served as base engine, but 4.8- and 5.3-liter V8s replaced the previous 5.0- and 5.7-liter engines, offering 25 and 15 more horsepower, respectively. Manual and 4-speed automatic transmissions were available. The automatic gained a Tow/Haul mode, which reduced the amount of shifting under heavy loads. New optional Autotrac 4-wheel drive could be left engaged on dry pavement, automatically engaging the front axle when rear-wheel slippage was detected. It could also be locked in 4WD High or Low range.