The GMC C3500HD headlight bulb size chart specifies high beam and low beam bulb sizes including H6054, 9005, H4701, 9006, and H4703 for this heavy-duty truck model. The replacement chart covers vehicle production years from 1991 to 2002 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 GMC C3500HD carries two distinct headlamp system types across its 1991-2002 model years: sealed beam units and halogen capsule assemblies. Each system requires entirely different bulb types, and the two are not interchangeable within the same housing.
The H6054 is a 5x7-inch rectangular sealed beam unit rated at 12V. It functions as both the high beam and low beam source within a single self-contained lens-and-filament assembly, meaning the entire unit is replaced rather than an internal bulb.
The H4701 and H4703 are 7-inch round sealed beam units, both rated at 12V, and both are also full replacement units rather than serviceable bulbs. These two types split the high beam and low beam roles respectively in the 1991 four-rectangular-headlamp configuration.
In halogen capsule headlamp configurations, the high beam position uses the 9005 bulb, a single-filament halogen type with a P20d base rated at 12V and 65W. The low beam position uses the 9006, a single-filament halogen type with a P22d base rated at 12V and 55W.
The 9005 and 9006 bulbs share similar physical profiles but have different base types, P20d and P22d respectively, which prevents cross-installation between the high and low beam sockets without modification.
The 1991 model year of the C3500HD is the only year in the specifications that lists three distinct high beam options and three distinct low beam options, reflecting the availability of two-rectangular, four-rectangular, and halogen capsule headlamp configurations simultaneously.
All bulb types listed across the specifications conform to ANSI standards applicable in both the United States and Canada, placing them within a standardized sizing and performance framework shared across many North American vehicle applications.
From 1992 onward, the four-rectangular sealed beam configuration using H4701 and H4703 units is absent from the specifications, leaving the H6054 as the sole sealed beam option alongside the halogen capsule variants.