The White/GMC WCL uses 1157 bulb size for both front and rear turn signal applications. Replacement chart data covers 1988 to 1993 production 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 WCL uses the 1157 bulb for both front and rear turn signals across all listed model years from 1988-1993.
The 1157 is an ANSI-standardized bulb type recognized across the United States and Canada.
As a dual-filament bulb, the 1157 contains two separate filaments within a single envelope, allowing it to serve two distinct lighting functions from one unit.
The 1157 operates on a 12-volt electrical system, consistent with standard automotive voltage.
Its two filaments are rated at 21 watts and 5 watts respectively, with the higher-wattage filament typically serving the turn signal or brake function and the lower-wattage filament serving a running light function.
The 1157 uses a BAY15d bayonet base, which is an offset dual-contact base design that prevents incorrect insertion by positioning the two base pins at different heights.
The uniform use of the 1157 across both front and rear positions on the WCL means a single bulb type serves all four turn signal housings on the vehicle.
Because the BAY15d base is offset, it is not interchangeable with single-contact or symmetrical dual-contact bayonet bases, even when the physical size of the bulb appears similar.