GMC W5500 Forward Headlight Bulb Size

Additional Notes

• The GMC W5500 Forward uses six distinct sealed beam bulb types across its headlight specifications: H4651, H4656, H5001, H5006, H6024, and H6054. 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 GMC W5500 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 H4651 and H4656 are both 4x6-inch rectangular sealed beam units. The H4651 serves the high beam position while the H4656 serves the low beam position. Despite their near-identical physical form, the two types are not interchangeable due to differing beam patterns engineered for their respective functions.
• The H5001 and H5006 are both 4-inch square sealed beam units assigned to the Tiltmaster variant. The H5001 covers the high beam and the H5006 covers the low beam. As with the 4x6-inch pair, the shared physical format does not make them functionally interchangeable.
• The H6054 is a 5x7-inch rectangular sealed beam unit used in configurations with two rectangular headlamps, serving both the high and low beam positions within that setup. The H6024 is a 7-inch round sealed beam unit used in configurations with two round headlamps, also covering both beam positions.
• The Tiltmaster variant of the W5500 Forward carried distinct bulb requirements separate from the two-rectangular-headlamp and two-round-headlamp configurations. From 1997-2001, the Tiltmaster exclusively used the H4651 for high beam and H4656 for low beam, while in 1996 and earlier it used H5001 and H5006 respectively.
• For model years 1988-1995, the W5500 Forward with four rectangular headlamps used the H4651 for high beam and H4656 for low beam, the same types later adopted by the Tiltmaster variant from 1997 onward. Vehicles with two rectangular headlamps used the larger H6054 for both beam positions across that same period.
• The round headlamp configurations, using H6024 for both beam positions, are documented for 1988, and 1991-1995, with the exception of 1989-1990 where no round headlamp variant appears in the specifications.