Large disc/drum brakes and a maximum payload capability of over 4,000 pounds are traits of the 1999 GMC Sierra 3500. Powered by a 255 hosrepower 5.7 liter Vortec V-8 as a base engine, a 290 horsepower, 7.4 liter V-8 and a 6.5 liter turbodiesel engine can also be ordered on the 1999 GMC Sierra 3500. Available in rear-wheel and four-wheel drive configurations with even a dual rear wheel version, wheel motion is fed by a standard five-speed manual or an optional four-speed automatic transmission. Interior comfort is defined from the 1999 Sierra 3500 SL, SLE and SLT trim levels. With basic vinyl seating completing the SL model, cloth upholstery, cassette player, cruise control and air conditioning are added equipment to the 1999 GMC Sierra 3500 pickup. On SLT models, leather seating adds an extra touch of comfort to this professional grade vehicle. Optional equipment found on the 1999 GMC Sierra 3500 lists a locking differential and CD player. For extra safety with either rear or four-wheel drive, 1999 GMC Sierra 3500 includes four-wheel anti-lock braking system as standard.