The GMC R3500 front turn signal requires a 2357NA or 2057NA bulb size, while the rear turn signal uses a 3057 or 2057 bulb size. The replacement chart covers 1987 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 GMC R3500 front turn signal uses the 2357NA bulb for model years 1988-1991, while the 1987 model year uses the 2057NA instead.
The 2357NA and 2057NA are both ANSI-standard dual-filament bulbs rated at 12V with a 26.9W high-filament and 8W low-filament output, sharing the BAY15d bayonet base.
Both the 2357NA and 2057NA feature natural amber glass, which produces the amber turn signal color directly from the bulb rather than relying on a colored lens.
The 2057NA is noted as a brighter variant of the 1157, meaning it produces greater light output than the 1157 while maintaining the same BAY15d bayonet base fitment.
The rear turn signal on the GMC R3500 transitions from the 2057 bulb in 1987-1989 to the 3057 bulb in 1990-1991, indicating a socket or housing change between those model years.
The 3057 is a wedge-type bulb in a T25 form factor, which is physically incompatible with the BAY15d bayonet socket used by the 2057, 2057NA, and 2357NA bulbs.
The 3057 is rated at 12V with a 27W high-filament and 7W low-filament output, placing its wattage close to but not identical to the 26.9W/8W rating of the BAY15d-based bulbs used elsewhere on the vehicle.
The 2057 shares the same BAY15d bayonet base and 26.9W/8W rating as the 2057NA, with the NA suffix designating the natural amber glass version of that bulb.