The Hino GC17 uses an H4651 bulb size for high beam headlight operation and an H4656 bulb size for low beam headlight operation. The replacement chart covers vehicle production years spanning 1990 to 1991 with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The H4651 and H4656 are both ANSI-standardized sealed beam units used across North American markets, meaning their physical and electrical specifications are governed by a shared industry standard rather than proprietary manufacturer designs.
Both bulb types take the form of a 4x6-inch rectangular sealed beam unit, a format in which the lens, reflector, and filament are fused into a single glass assembly.
Because the filament is enclosed within the sealed glass housing, neither the H4651 nor the H4656 supports bulb replacement independent of the housing. The entire unit is replaced when the light fails.
Both units operate on a 12V electrical system, consistent with standard automotive voltage.
The Hino GC17 uses the H4651 for high beam and the H4656 for low beam across the 1990-1991 model years, meaning the two functions are served by physically similar but electrically distinct sealed beam units.
The H4651 and H4656 share the same 4x6-inch rectangular form factor, but they are not interchangeable between high and low beam positions due to differences in their filament and beam pattern configurations.