GMC R1500 Suburban Headlight Bulb Size

The GMC R1500 Suburban headlight bulb specifications include high beam sizes H6054, H4701, and H4651, along with low beam sizes H6054, H4703, and H4656 in multiple bulb configurations. The replacement chart covers 1987 through 1991 model years with corresponding bulb size data for each production year.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

High Beam Headlight

Years	Bulb Size
1989-1991	H6054 (With 2 Headlamps)
1989-1991	H4701 (With 4 Headlamps)
1987-1988	H6054 (With 2 Headlamps)
1987-1988	H4651 (With 4 Headlamps)

Low Beam Headlight

Years	Bulb Size
1989-1991	H6054 (With 2 Headlamps)
1989-1991	H4703 (With 4 Headlamps)
1987-1988	H6054 (With 2 Headlamps)
1987-1988	H4656 (With 4 Headlamps)

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). 5x7-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H6054
ANSI standard (US & Canada). 7-inch round sealed beam unit, variant. Not a replaceable bulb — the entire unit is replaced. 12V.	H4701
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4651
ANSI standard (US & Canada). 7-inch round sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4703
ANSI standard (US & Canada). 4x6-inch rectangular sealed beam unit. Not a replaceable bulb — the entire unit is replaced. 12V.	H4656

Other Locations

Additional Notes

The GMC R1500 Suburban uses sealed beam headlight units across all listed model years (1987-1991), meaning the entire lens-and-filament assembly is replaced as one unit rather than swapping an internal bulb.
All five bulb types found in these specifications, H6054, H4701, H4651, H4703, and H4656, conform to ANSI standards recognized in both the United States and Canada, and all operate at 12V.
The H6054 is a 5x7-inch rectangular sealed beam unit and serves as the sole headlight type on 2-headlamp configurations across every listed year, functioning as both the high beam and low beam in that setup.
On 4-headlamp configurations, the high beam and low beam positions use physically distinct sealed beam units, which means the two pairs are not interchangeable with each other even though they may share a similar round or rectangular form factor.
For 4-headlamp configurations in 1989-1991, the high beam position uses the H4701, a 7-inch round sealed beam unit, while the low beam position uses the H4703, also a 7-inch round sealed beam unit. Though similar in shape, these are separate part numbers serving separate functions.
The 4-headlamp configuration for 1987-1988 uses 4x6-inch rectangular sealed beam units: the H4651 for high beam and the H4656 for low beam. These two types share the same physical size but are not interchangeable due to their differing beam patterns.
A change in the 4-headlamp bulb types occurred between the 1988 and 1989 model years, with the rectangular H4651 and H4656 units being replaced by the round H4701 and H4703 units respectively, while the 2-headlamp H6054 remained unchanged throughout 1987-1991.