The GMC G2500 brake light requires 2057 and 1157 bulb sizes depending on the specific production period for the vehicle. Available information covers the span from 1979 through 1995.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC G2500 brake light circuit relies on dual-filament bulbs across all listed model years, reflecting the standard practice of combining stop and tail light functions within a single bulb housing.
The 2057 bulb is specified for the GMC G2500 brake lights from 1983-1995. It uses a BAY15d bayonet base and operates at 12V with a dual-filament output of 26.9W on the high-intensity filament and 8W on the low-intensity filament.
The 1157 bulb is specified for model years 1979-1982. It shares the same BAY15d bayonet base as the 2057 but operates at lower wattage, rated at 21W and 5W across its two filaments.
Because the 2057 and 1157 bulbs share the BAY15d bayonet base, they are physically interchangeable in terms of socket fitment. However, the two bulbs differ in filament wattage, which affects light output intensity.
The center high mount stop light (CHMSL) on the G2500 uses the 921 bulb for model years 1988-1995. The 921 is a single-filament wedge-type bulb rated at 12V and 16W, designated as a T15 in the wedge base family.
The 921 wedge bulb used in the CHMSL is not interchangeable with the BAY15d bayonet-base bulbs used in the standard brake light positions, as the two types use entirely different mounting and contact systems.
The 2057 bulb produces a notably higher high-beam filament output than the 1157, with 26.9W compared to 21W, while the low-beam filament of the 2057 at 8W is also higher than the 1157's 5W rating.
All three bulb types specified across the G2500 brake light positions conform to ANSI standards recognized in both the United States and Canada.