GMC W6500 Forward front and rear turn signal bulbs use 1073, 2057, or 1157 size specifications. The replacement chart covers vehicle production spanning 1987 to 1996.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1073 bulb is the most frequently specified size across the GMC W6500 Forward turn signal data, appearing in both front and rear positions across multiple model years for the Tiltmaster configuration. It is a single-filament bulb rated at 12V and 13W, using a BA15s bayonet base.
The 2057 and 1157 bulbs are both dual-filament types sharing the BAY15d bayonet base, though they differ in wattage output. The 2057 operates at 26.9W on its high filament and 8W on its low filament, while the 1157 operates at 21W and 5W respectively.
Because the 1073 uses a BA15s single-contact base and the 2057 and 1157 use a BAY15d dual-contact base, these bulb types are not interchangeable despite their physical similarity as bayonet-style bulbs.
The W6500 Forward specifications list distinct bulb sizes depending on the vehicle configuration within the same model year, meaning the Tiltmaster and Medium Duty variants of the same year can require different bulbs in the same lighting position.
In the 1987 front turn signal position, three separate bulb sizes are listed: 2057, 1157 for the Medium Duty, and 1073 for the configuration with four round headlamps, indicating that body or trim configuration directly affects bulb fitment for that year.
The 1157 bulb appears exclusively in Medium Duty configurations within the front and rear turn signal data, covering model years 1987-1991 for the front and 1987-1989 plus 1991 for the rear.
The 2057 bulb appears in both Tiltmaster and Medium Duty configurations across various years, as well as in the 1988 front position without a sub-configuration label, making it the dual-filament bulb with the broadest fitment range in these specifications.
In the 1994 rear turn signal position, the Tiltmaster configuration uses a 2057 bulb, while the same vehicle's 1994 front turn signal uses a 1073 bulb, showing that front and rear positions do not always share the same bulb size within a given year.