The GMC G1500 brake light utilizes 1034, 1157, and 2057 bulb sizes across the various production periods listed in the provided data. Information covers the span from 1964 through 1995 for the specified vehicle components.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC G1500 brake light circuit relies on the 2057 bulb across the 1983-1995 model years, making it the most widely specified bulb in these brake light specifications.
The 2057 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V and 26.9W on its high-filament circuit and 8W on its low-filament circuit, which allows it to serve both brake and running light functions from a single unit.
The 1157 bulb shares the same BAY15d bayonet base as the 2057 and carries the same dual-filament design, but its high-filament wattage is rated at 21W rather than 26.9W, making the two types physically interchangeable in base fitment while differing in output.
The GMC G1500 used the 1157 bulb for brake lights across the 1979-1982 model years.
The 1034 bulb, specified for the 1964-1966 model years, also uses the BAY15d bayonet base and shares the same 12V, 21W/5W rating as the 1157, though the two are listed as distinct ANSI types.
Because the 2057, 1157, and 1034 all share the BAY15d bayonet base, physical installation across these types is mechanically compatible, though wattage differences mean they are not electrically identical substitutes.
The center high mount stop light on the GMC G1500 uses the 921 bulb for the 1988-1995 model years.
The 921 is a single-filament wedge-type bulb in a T15 form factor, rated at 12V and 16W, and its wedge base is not interchangeable with the BAY15d bayonet base used by the brake light bulbs specified elsewhere in these data.