GMC B6000 front and rear side marker bulbs utilize 1157, 194, and 1895 bulb sizes depending on location and model year. The replacement chart covers 1980 to 1991 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 194 bulb is the most frequently specified size across both front and rear side marker positions on the GMC B6000, appearing in the majority of model years from 1980 through 1991.
The 194 is a miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W, and is classified under the ANSI standard applicable to the US and Canada.
The 1157 bulb is a dual-filament type with a BAY15d bayonet base, rated at 12V with a 21W main filament and a 5W secondary filament. Its dual-filament construction distinguishes it from the single-filament 194 and 1895 bulbs also referenced in these specifications.
The 1895 is a miniature wedge bulb in the T5 form factor, rated at 12V and 0.9W, making it the lowest-wattage bulb specified across all side marker positions on the GMC B6000.
The front side marker on the GMC B6000 uses the 1157 for most Medium Duty configurations in 1980, 1987, and 1989-1991, while the 194 applies to Medium Duty trims equipped with 2 rectangular headlights in 1980 and 1987.
The 1157 and 194 are not interchangeable on the front side marker of the 1987 B6000, as the correct fitment depends on whether the vehicle has 2 rectangular headlights, making headlight configuration a determining factor in bulb selection.
The rear side marker on the 1980 B6000 Heavy Duty trim uses the 1895, while the Medium Duty trim for the same year uses the 194, indicating that duty rating directly affects rear side marker bulb fitment for that model year.
The 1157 appears in the rear side marker position only for the 1985 B6000 Medium Duty, a notable departure from the 194 that is otherwise standard across the rear side marker for the surrounding model years.
The BAY15d bayonet base of the 1157 is physically incompatible with the wedge-style sockets used by the 194 and 1895, meaning these bulb types cannot be substituted for one another regardless of voltage compatibility.
All three bulb types specified for the GMC B6000 side markers, the 1157, 194, and 1895, are rated at 12V and conform to ANSI standards recognized in both the US and Canada.