GMC W5500 Forward front and rear turn signal bulbs use 1157, 1073, or 2057 size specifications. The replacement chart covers vehicle production years spanning 1988 to 2001.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The three bulb types specified across the GMC W5500 Forward turn signal positions are the 1157, 1073, and 2057, all of which conform to ANSI standards recognized in the United States and Canada.
The 1157 and 2057 are dual-filament bulbs sharing the BAY15d bayonet base, meaning they each carry two separate filaments within a single envelope and use the same base configuration.
The 2057 operates at 26.9W on its primary filament and 8W on its secondary, making it the higher-wattage dual-filament option compared to the 1157, which runs at 21W and 5W respectively.
The 1073 is a single-filament bulb with a BA15s bayonet base, operating at 12V and 13W. Its base type differs from both the 1157 and 2057, which use the BAY15d base, making the 1073 physically non-interchangeable with those two types.
Because the BAY15d base on the 1157 and 2057 is physically the same, a socket designed for one could accept the other, though the wattage difference between the two means they are not electrically equivalent replacements.
The GMC W5500 Forward (Tiltmaster) front turn signal used the 1073 from 1988-1996, with the exception of 1989 and 1993, which specified the 2057 instead.
The Tiltmaster front turn signal shifted to the 1157 for the 1997-2001 model years, representing a change from the single-filament 1073 to a dual-filament configuration.
In model years where both a Tiltmaster and a Medium Duty sub-variant are listed, the two sub-variants do not always share the same bulb type, indicating that fitment is sub-variant-specific and not interchangeable across configurations within the same year.
The rear turn signal specifications for the Tiltmaster sub-variant show the 2057 appearing in 1988, 1989, and 1994, while the 1073 appears in other years within the same range, reflecting non-uniform bulb usage across the rear position over time.
The 1991 and 1990 rear turn signal entries carry no sub-variant label and specify the 2057, distinguishing them from the labeled Tiltmaster and Medium Duty entries found in surrounding years.