GMC C1500 Suburban Back Up Light Bulb Size

Additional Notes

• The GMC C1500 Suburban back up light specifications cover model years 1979-1986 and 1992-1999, spanning three distinct bulb types across that range.
• The 2456 is the most frequently specified back up light bulb in these records, appearing across seven model years: 1992-1995 and 1997-1999.
• The 2456 is an ANSI-standard festoon bulb rated at 12 volts, classified as a specialty application type. Festoon bulbs are cylindrical in form and seat by contact pressure at each end rather than using a base socket.
• The 1156 is the second most common bulb in these specifications, covering eight model years from 1979-1986. It uses a BA15s bayonet base, a single-contact mount that locks into its socket with a twist, and is rated at 12 volts and 21 watts.
• The 3156 appears exclusively for the 1996 GMC C1500 Suburban, making it the least common bulb type in this specification set. It is a single-filament wedge bulb in the T25 form factor, rated at 12 volts and 27 watts.
• All three bulb types, the 2456, 3156, and 1156, conform to ANSI standards applicable in both the United States and Canada.
• The 3156 wedge bulb used in 1996 operates at 27 watts, while the 1156 bayonet bulb used in 1979-1986 operates at 21 watts. These two types are not interchangeable due to differences in base design, wattage, and physical form factor.
• The 1996 model year stands as the sole exception within the 1992-1999 range, where all surrounding years use the 2456 festoon bulb. Substituting a 3156 wedge bulb in place of a 2456 festoon, or vice versa, would require a socket adapter due to their incompatible mounting designs.