GMC 370 front and rear turn signal bulbs utilize 1156, 1073, and 1129 bulb sizes across different model configurations. The replacement chart covers 1951 through 1959 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 1129 bulb is the most frequently specified type across the GMC 370's turn signal fitment data, covering both front and rear positions for the 1951-1955 model years.
The 1129 is a dual-filament bulb rated at 12V and 21/5W, using a BAY15d bayonet base. The dual-filament design allows a single bulb to serve two lighting functions at different wattage levels.
The 1073 bulb appears in both the front and rear turn signal positions for the 1956-1958 GMC 370, making it the sole bulb type required across both positions during those years.
The 1073 is a single-filament bulb rated at 12V and 13W with a BA15s bayonet base. It is described as a lower wattage variant of the 1156.
For the 1959 GMC 370, the front and rear turn signal positions require different bulb types: the 1156 at the front and the 1034 at the rear.
The 1156 is a single-filament bulb rated at 12V and 21W with a BA15s bayonet base, and it is specified only for the 1959 front turn signal position.
The 1034 is a dual-filament bulb rated at 12V and 21/5W with a BAY15d bayonet base, and it is specified only for the 1959 rear turn signal position.
The 1129 and 1034 share the same BAY15d base and voltage and wattage ratings, as both are listed as variants of the 1157, though they are not specified interchangeably within these fitment records.
The 1156 and 1073 share the same BA15s bayonet base type, but their wattage ratings differ at 21W and 13W respectively, which means socket compatibility does not indicate functional interchangeability.
All four bulb types in these specifications conform to ANSI standards applicable in the United States and Canada.