GMC C3500HD front turn signal bulbs use 2357NA or 1157 size, while rear turn signal bulbs use 3057 or 1157 size. The replacement chart covers 1991 to 2002 model 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 C3500HD front turn signal position uses the 2357NA bulb across the 1991-2002 model years, with the sole exception of the 1992 Medium Duty variant, which takes the 1157 instead.
The 2357NA is a dual-filament bulb rated at 12V with a 26.9W high filament and an 8W low filament. It features a BAY15d bayonet base and natural amber glass, meaning the amber color is built into the glass rather than produced by a clear bulb in a colored housing.
The natural amber glass of the 2357NA distinguishes it from a standard 2357, which is otherwise electrically and mechanically identical. Substituting a clear 2357 for a 2357NA may affect the color output of the turn signal if the lens housing is also clear.
The 1157 shares the same BAY15d bayonet base as the 2357NA but operates at lower wattages of 21W and 5W. Although both bulbs physically fit the same socket type, the difference in wattage means they are not direct equivalents in all applications.
The rear turn signal position on the GMC C3500HD uses two different bulb types depending on the model year. The 1157 is specified for 1991-1994, 1996-1997, and the 1992 Medium Duty variant, while the 3057 is specified for 1995 and 1999-2002.
The 3057 is a dual-filament wedge bulb in the T25 form factor, rated at 12V with a 27W high filament and a 7W low filament. Unlike the 1157 and 2357NA, it uses a wedge base rather than a BAY15d bayonet base, making it physically incompatible with sockets designed for those bulbs.
All three bulb types listed in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating standardized electrical and photometric performance across those markets.
The 1998 rear turn signal position uses the 3057, while the 1997 and 1996 positions use the 1157. These adjacent model years require different bulb types with non-interchangeable base designs, making year-specific verification necessary before replacement.
The 1991 and 1992 model years carry a Medium Duty designation in both the front and rear turn signal entries. The 1992 Medium Duty front position specifies the 1157, which differs from the 2357NA used in the 1991 Medium Duty front position despite both sharing the BAY15d base.
The dual-filament design present in all three bulb types serves two circuit functions within a single bulb, typically providing both a running light function on the lower-wattage filament and a turn or brake signal function on the higher-wattage filament.