The White/GMC WIM uses 1157 bulb size for both front and rear turn signal applications. The replacement chart covers 1988 to 1994 model years 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 White/GMC WIM uses the 1157 bulb for both its front and rear turn signals across the 1988-1994 model years.
The 1157 is an ANSI-standardized bulb type recognized across the United States and Canada, meaning it conforms to a defined set of electrical and physical characteristics shared by all compliant manufacturers.
The 1157 is a dual-filament bulb, which means it contains two separate filaments within a single housing, allowing it to serve two distinct lighting functions from one unit.
It operates on a 12-volt electrical system and carries a wattage rating of 21W for the primary filament and 5W for the secondary filament, with the higher-wattage filament typically assigned to the turn signal function and the lower to a parking or running light function.
The 1157 uses a BAY15d bayonet base, a two-pin offset base design that physically prevents incorrect insertion, as the two pins are positioned at different heights to ensure proper filament alignment within the socket.
Because the same bulb type is specified for both the front and rear turn signal positions on the White/GMC WIM, a single 1157 bulb serves as a direct replacement for either location without substitution or adaptation.