GMC W6500 Forward Headlight Bulb Size

Additional Notes

• The GMC W6500 Forward uses six distinct sealed beam bulb types across its headlight specifications: H5001, H5006, H6024, H6054, H4651, and H4656. All six conform to ANSI standards recognized in both the United States and Canada and operate on 12V electrical systems.
• Every bulb type listed for the W6500 Forward is a sealed beam unit, meaning the lens, reflector, and filament are fused into a single assembly. When a filament fails, the entire unit requires replacement rather than an internal bulb swap.
• The H6054 and H6024 are the most broadly specified bulb types across the W6500 Forward's headlight configurations. The H6054 is a 5x7-inch rectangular sealed beam used for high and low beam in two-rectangular-headlamp configurations, while the H6024 is a 7-inch round sealed beam serving the same dual role in two-round-headlamp configurations.
• The Tiltmaster variant of the GMC W6500 Forward uses a separate pair of sealed beam types exclusive to that configuration: the H5001, a 4-inch square unit for high beam, and the H5006, a 5.75-inch round unit for low beam. These two types do not appear in any other headlamp configuration listed in the specifications.
• Vehicles equipped with four rectangular headlamps use the H4651 for high beam and the H4656 for low beam. Both are 4x6-inch rectangular sealed beam units, making them physically identical in size despite serving different beam functions. Substituting one for the other would result in incorrect beam output.
• The H6054 sealed beam is the only type that functions as both a high beam and a low beam unit within the same configuration. In two-rectangular-headlamp setups, it covers both roles, which is a characteristic of certain sealed beam systems where a single lamp type handles dual-beam output.
• The H6024 round sealed beam is specified for 1987-1988 and 1992-1995 model years, but not for 1989-1991 or 1996. This reflects configuration-level fitment variation rather than a universal round-headlamp option across all years.
• Because the H4651 and H4656 share the same 4x6-inch physical format, correct installation depends on matching the beam designation rather than the physical size of the unit. Misidentification between these two types is a known fitment risk in four-headlamp rectangular configurations.