GMC Sierra Brake Bulb Size

Additional Notes

• The 7443 is the most frequently specified brake bulb across the GMC Sierra lineup, appearing in the main brake position across model years 2019-2020, 2022, and in both 2023-2024 for the 3500 HD trim. It is a dual-filament T20 wedge bulb rated at 12V with a 21W high-filament and 5W low-filament output.
• The 7444NA, used on the Sierra 1500 for 2023-2024, is technically identical to the 7443 in filament count, voltage, and wattage, but its glass envelope is tinted natural amber rather than clear. This tint produces an amber light output without requiring an amber lens on the vehicle.
• The 7444, specified for model years 2015-2018 and the 2014 Sierra 1500, shares the same T20 wedge form factor and 12V, 21W/5W dual-filament rating as the 7443. The numeric difference between 7443 and 7444 reflects a distinct ANSI part number, and the two are not guaranteed to be interchangeable without confirming fitment for a specific model year.
• The 3047, used across model years 2007-2013 and on the 2014 Sierra 3500 HD, is a single-filament T25 wedge bulb rated at 12V and 27W. Unlike the dual-filament bulbs used in later years, it carries only one filament, meaning it does not serve a combined brake-and-tail function through separate filaments.
• The 3157, specified for model years 1999-2006, is a dual-filament T25 wedge bulb rated at 12V with a 27W high filament and 7W low filament. Its T25 body is physically larger than the T20 body used by the 7443 and 7444 families, making the two groups dimensionally incompatible despite both being wedge-base designs.
• The 921 bulb is specified for the Center High Mount Stop Light position on every Sierra model year from 1999 through 2024. It is a single-filament T15 wedge bulb rated at 12V and 16W, and its application has remained unchanged across the entire span covered by these specifications.
• The 2014 Sierra is a split-fitment year for the main brake position: the 1500 uses the 7444 while the 3500 HD uses the 3047. These two bulbs differ in both body size and filament count, and one cannot substitute for the other.
• In the Outer Brake position for 2017-2019, Sierra 3500 HD trucks equipped with the Chassis Cab package (option code ZW9) use the 1156, a single-filament bulb with a BA15s bayonet base rated at 12V and 21W. The same years without the Chassis Cab package use the 7443 wedge bulb instead. The bayonet base of the 1156 is physically incompatible with the wedge socket of the 7443.
• The 1157, used on the 2021 Sierra for the main brake position, is a dual-filament bulb with a BAY15d bayonet base rated at 12V, 21W/5W. Its bayonet base type differs from the wedge base of the 7443 and 7444 used in surrounding model years, making it a non-interchangeable fitment despite sharing the same voltage and wattage ratings.
• For the 2018 Sierra 1500 Outer Brake position, the 7443 is specified only for vehicles without the Appearance Package (excluding option code GAT). No wedge-base bulb is listed for 1500 trims equipped with that package, as those entries fall outside the scope of these specifications.