Pontiac GTO front and rear turn signal bulbs utilize sizes 1157NA, 1034NA, 1157, and 1156NA depending on generation and position. The replacement chart covers 1964 through 2006 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 front turn signal positions on the Pontiac GTO use dual-filament bulbs across all listed model years, with the BAY15d bayonet base shared by the 1157NA, 1034NA, and 1157 types.
The rear turn signal positions on the 2004-2006 GTO use the 1156NA, a single-filament bulb with a BA15s bayonet base, which is physically and electrically distinct from the dual-filament 1157 used in rear positions on the 1964-1973 models.
Because the BA15s and BAY15d bases are not interchangeable, the 1156NA specified for the 2004-2006 rear position cannot be substituted with any of the dual-filament types listed for other positions or years.
The 1157NA and 1034NA are both dual-filament, 12V, 21W/5W bulbs sharing the BAY15d base, with the 1034NA described as a variant of the 1157 series. The practical distinction between them in these specifications is the bulb type designation rather than a difference in voltage or wattage rating.
The natural amber glass on the 1157NA, 1034NA, and 1156NA types produces an amber output from the bulb itself, whereas the standard 1157 has clear glass and relies on a colored lens to produce the required amber signal color.
The front turn signal on the Pontiac GTO alternates between the 1157NA and 1034NA across model years, with the 1034NA appearing on the 1967-1968, 1970, 1972, and 2004 models, and the 1157NA on the 1965-1966, 1969, 1971, and 2005-2006 models.
The 1973 front turn signal is the only front position in the listed specifications that uses the standard clear-glass 1157 rather than an NA-suffix bulb, while the rear position for that same year also uses the 1157, consistent with all rear positions from 1964-1973.
The rear turn signal on the 1964-1973 GTO uses the 1157 across all those model years without variation, making it the most consistent single fitment across any position in these specifications.
All four bulb types listed are ANSI standards applicable to both the United States and Canada, indicating regulatory compliance for turn signal use in both markets.
The dual-filament construction of the 1157, 1157NA, and 1034NA bulbs means a single bulb serves two brightness levels, a function relevant when a turn signal position also operates as a parking or running light.