The GMC W7500 Forward uses front and rear turn signal bulbs in sizes 1073, 2057, and 1157. The replacement chart covers vehicle production years from 1984 to 1996 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 GMC W7500 Forward front and rear turn signal specifications span model years 1984-1996, with multiple bulb sizes listed for many individual years due to trim and configuration variants within the same model year.
Three distinct bulb types appear across the W7500 Forward turn signal specifications: the 1073, the 2057, and the 1157. Each belongs to the ANSI standard series recognized in both the United States and Canada.
The 1073 is a single-filament bulb rated at 12V and 13W, fitted with a BA15s bayonet base. Its single filament means it serves one lighting function only, making it unsuitable as a direct substitute in sockets designed for dual-filament operation.
The 2057 and 1157 are both dual-filament bulbs sharing the BAY15d bayonet base, which offsets its two pins at different heights to prevent incorrect insertion. Despite this shared base type, the two bulbs are not electrically identical and are not interchangeable without consequence.
The 2057 operates at 26.9W on its high-intensity filament and 8W on its low-intensity filament, while the 1157 operates at 21W and 5W respectively. The 2057 draws notably more current on its primary filament, which is a relevant consideration for socket and wiring load ratings.
The Tiltmaster variant of the GMC W7500 Forward used the 1073 for both front and rear turn signals in 1995-1996, representing a single-filament application at those positions for that configuration.
In 1992, the GMC W7500 Forward (Tiltmaster) used the 1073 for both front and rear turn signals, while the Medium Duty variant used the 2057 at the front and the 1157 at the rear, illustrating that front and rear positions did not always share the same bulb type within a given configuration.
The 1987 model year carries three separate front turn signal entries: the 1157 for the Medium Duty variant, the 1073 as a general listing, and the 2057 for vehicles with two round headlamps. The headlamp configuration is used as a distinguishing fitment condition in that year.
The 1986 front turn signal specifications include the 1073 specifically for vehicles with four round headlamps, while the 2057 appears as a separate general entry for the same year, indicating that headlamp count directly determines the correct front turn signal bulb in that model year.
The BA15s base of the 1073 and the BAY15d base of the 2057 and 1157 are physically distinct. The BA15s has a single contact pin, while the BAY15d has two offset pins, meaning bulbs from these two base families cannot be physically seated in each other's sockets.