What type of freon is used in a 1997 Chevy silverado?

1997 Chevy Silverado trucks most likely used R-134a refrigerant in their air conditioning systems. While R-12 was used in older vehicles, R-134a largely replaced it by the mid-1990s due to environmental concerns. However, it's always best to check the sticker on the underside of the hood of your specific vehicle to be absolutely certain.