The GMC R1500 Suburban front turn signal requires a 3057NA or 2057NA bulb size, while the rear turn signal uses a 2057 bulb size. The replacement chart covers 1987 through 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 R1500 Suburban front turn signal uses the 3057NA bulb for 1989-1991 and the 2057NA bulb for 1987-1988, meaning the front turn signal position saw a bulb type change between the 1988 and 1989 model years.
The 3057NA is a dual-filament wedge bulb of the T25 type, operating at 12V with a high-beam filament rated at 27W and a low-beam filament rated at 7W.
The 2057NA uses a BAY15d bayonet base rather than a wedge mount, which makes it physically incompatible with sockets designed for the T25 wedge-style 3057NA despite both bulbs serving the same front turn signal function on this vehicle across different model years.
Both the 3057NA 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 described as a brighter variant of the 1157 bulb, sharing the same BAY15d bayonet base but offering higher output, with wattage rated at 26.9W and 8W across its two filaments.
The rear turn signal on the GMC R1500 Suburban uses the 2057 bulb consistently across all listed model years, 1987-1991.
The 2057 and 2057NA share identical electrical ratings of 12V, 26.9W/8W and the same BAY15d bayonet base, with the only difference being that the 2057NA incorporates natural amber glass while the 2057 does not.
Because the 2057NA and 2057 share the same base type and wattage, the front turn signal socket on 1987-1988 models is electrically and physically compatible with the clear 2057 used in the rear, though the amber glass coating of the 2057NA would be absent if substituted.
All three bulb types listed in these specifications, the 3057NA, 2057NA, and 2057, conform to ANSI standards applicable in both the United States and Canada.
The dual-filament design present in all three bulb types allows a single bulb to serve both a higher-intensity function and a lower-intensity function within the same housing, which is typical in combined turn signal and parking light applications.