The Kenworth C550 front side marker uses 904 or 1157 bulb sizes, while the rear side marker requires 904 or 67 bulb sizes. The replacement chart covers 1986 to 1994 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Kenworth C550 uses three distinct bulb types across its front and rear side marker positions: the 904, 1157, and 67.
The 904 is a T10 miniature wedge bulb rated at 12V and 8W, conforming to ANSI standards recognized in both the US and Canada.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W filament configuration, also an ANSI-standard type for the US and Canada.
The 67 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 8W, and is considered a lower wattage variant of the 1156 bulb family.
The 1157 and 67 use different bayonet base types, BAY15d and BA15s respectively, making them physically non-interchangeable despite both using bayonet-style mounting.
The 904 wedge base and the 67 BA15s bayonet base are also non-interchangeable, as their mounting systems are fundamentally different, even though both are rated at 8W.
On the Kenworth C550, the front side marker used the 1157 from 1988-1993, with the 904 appearing in 1994 and 1987, and the 1157 again in 1986.
The rear side marker used the 904 consistently from 1987-1994, while the 1986 model year used the 67 in that position.
The dual-filament design of the 1157 draws significantly more power on its primary filament at 21W compared to the 8W single-filament ratings of both the 904 and 67.
The front and rear side marker positions share the same bulb type only in 1994 and during 1987-1993 on the rear, meaning the two positions do not consistently use matching bulbs across all model years.