GMC Caballero high beam and low beam headlight bulbs utilize H4651, H6054, H4652, and H4656 bulb sizes depending on configuration. The replacement chart covers 1978 to 1987 model year data 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 Caballero uses four distinct sealed beam headlight types across its 1978-1987 model years: H4651, H4652, H4656, and H6054. All four are ANSI-standardized units rated at 12V and are sold and replaced as complete assemblies rather than as individual bulbs.
The H6054 is a 5x7-inch rectangular sealed beam unit and is the physically larger of the two housing formats found in the Caballero. The H4651, H4652, and H4656 are all 4x6-inch rectangular sealed beam units.
The GMC Caballero (1978-1981) used the H6054 for both high beam and low beam positions, meaning a single sealed beam type served both functions during those model years.
The H4652 is described as a variant of the H4651. Both share the same 4x6-inch rectangular sealed beam housing and ANSI classification, though they are designated for different beam functions: H4651 for high beam and H4652 for low beam.
The low beam position of the Caballero used three different sealed beam types across the 1982-1987 range. The H4652 was fitted in 1982 and again in 1986-1987, while the H4656 was used in 1983-1985, indicating that the low beam specification was not uniform across those years even though all units share the same 4x6-inch housing format.
Because the H4651, H4652, and H4656 all occupy the same 4x6-inch rectangular housing, physical fitment alone does not confirm interchangeability. Each carries a distinct ANSI designation corresponding to a specific beam function, and substituting one for another risks incorrect beam output for the intended position.
All sealed beam types listed for the Caballero conform to ANSI standards recognized in both the United States and Canada, meaning the specifications apply uniformly across both markets without regional variation.
Because all headlight units across the full 1978-1987 Caballero range are sealed beam assemblies, there is no separate bulb to source or socket to service. Replacement involves removing and installing the entire sealed beam unit as a single component.