GMC Caballero front turn signal bulbs utilize 2057NA, 1157NA, or 1034NA bulb sizes, while rear turn signal applications require 2057 or 1157 size bulbs. The replacement chart covers 1978 through 1987 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 Caballero uses five distinct bulb types across its front and rear turn signal positions from 1978-1987, all of which conform to ANSI standards applicable in both the United States and Canada.
Every bulb type specified for the Caballero's turn signals shares the BAY15d bayonet base, a dual-contact offset-pin fitting that physically distinguishes it from single-filament bases and ensures a secure, polarized connection.
All five bulb types are dual-filament designs, meaning each bulb serves two brightness levels within a single housing, typically supporting both a running light function and a higher-intensity turn or stop signal function.
The 2057 and 2057NA bulbs operate at 26.9W on the high filament and 8W on the low filament, while the 1157, 1157NA, and 1034NA bulbs operate at 21W and 5W respectively, making the 2057-series notably brighter on both filaments.
The "NA" suffix on the 2057NA, 1157NA, and 1034NA designations indicates natural amber glass, meaning the amber color is produced by the glass envelope itself rather than by an external coating or a colored lens.
The front turn signal of the GMC Caballero transitioned from the 1034NA in 1980-1981 to the 1157NA in 1982, and then to the 2057NA for the 1983-1987 model years.
The rear turn signal used the 1157 bulb from 1978-1982, then shifted to the 2057 for 1983-1987, a change that increased high-filament wattage from 21W to 26.9W at the rear position.
In 1982, the front and rear turn signals used different bulb types, with the front position requiring the 1157NA and the rear requiring the standard 1157, making them non-interchangeable despite sharing the same base type.
From 1983-1987, the front turn signal required the 2057NA while the rear required the 2057, a pairing that again reflects matching wattage ratings but differing glass treatments between the two positions.
The 1034NA is described as a variant of the 1157 and shares its 21W/5W rating and BAY15d base, though it carries a distinct ANSI designation and was specific to the front turn signal position on the 1980-1981 Caballero.