The Chevrolet Trailblazer turn signal requires a 7440NA bulb size for the specific lighting component located on the front or rear of the vehicle. Data for the bulb specifications covers the range from 2023 to 2023.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Chevrolet Trailblazer front turn signal uses the 7440NA bulb for the 2021 and 2024 model years, and the 3757NA bulb for the 2002-2005 model years.
The 7440NA is a single-filament T20 wedge bulb rated at 12V and 21W, built to the ANSI standard for the US and Canadian markets, and features natural amber glass to produce the required amber turn signal color without a separate amber lens.
The 3757NA is a dual-filament T25 wedge bulb rated at 12V, also conforming to the ANSI standard for the US and Canadian markets, and similarly uses natural amber glass for its color output.
The rear turn signal on the 2021 and 2024 Trailblazer also uses the 7440NA, making the front and rear turn signal bulbs identical for those model years.
For the 2002-2005 Trailblazer, the rear turn signal uses the 3157 rather than the 3757NA found at the front, meaning the front and rear positions require different bulbs on those model years.
The 3157 is a dual-filament T25 wedge bulb rated at 12V with a 27W high-filament and 7W low-filament output, conforming to the ANSI standard for the US and Canadian markets.
Because the 3757NA and 3157 are both dual-filament T25 wedge bulbs, their physical form is similar, but the 3757NA carries natural amber glass while the 3157 does not, making them functionally distinct for applications where lens color determines the amber output.
The 7440NA and the 3757NA are not interchangeable despite both carrying natural amber glass, as the 7440NA is a single-filament T20 wedge and the 3757NA is a dual-filament T25 wedge, with differences in filament count, base size, and wattage.