The White/GMC WHL uses 1157 bulb size for both front and rear turn signal applications. Replacement chart data spans 1988 to 1995 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 WHL uses the 1157 bulb for both its front and rear turn signals across the 1988-1995 model years.
The 1157 is a dual-filament bulb, meaning it carries two separate filaments within a single envelope, allowing it to serve two distinct lighting functions at different wattages.
It operates on a 12-volt electrical system and draws 21 watts on its high-intensity filament and 5 watts on its low-intensity filament.
The 1157 uses a BAY15d bayonet base, which features two offset pins at different heights to prevent incorrect insertion of a single-filament substitute.
The 1157 conforms to ANSI standards and is recognized across both the United States and Canada, reflecting its widespread adoption in North American vehicle manufacturing.
Because the front and rear turn signal positions share the same bulb type on the White/GMC WHL, a single replacement part covers both locations on the vehicle.
Substituting a single-filament 1156 bulb, which shares a similar bayonet form but has only one pin height and one filament, is not compatible with the BAY15d socket and would not seat correctly.