The Peterbilt 377 uses a 194 bulb size for front side marker applications and an 1816 bulb size for rear side marker applications. The replacement chart covers vehicle production spanning 1987 to 2001 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 Peterbilt 377 front side marker position uses the 194 bulb across all listed model years from 1987-2001, making it the only bulb type specified for that position throughout the entire production span covered.
The 194 is an ANSI-standardized miniature wedge bulb in the T10 form factor, rated at 12 volts and 3.78 watts.
The T10 designation refers to the bulb's tubular envelope width, expressed in eighths of an inch, placing it in the smaller end of the miniature wedge category.
The rear side marker position on the Peterbilt 377 uses the 1816 bulb for model years 1987-1997.
The 1816 is also an ANSI-standardized miniature wedge bulb, though it carries the T3.25 form factor designation, which reflects a narrower envelope than the T10 used at the front.
The 1816 operates at 12 volts and 4 watts, a marginally higher wattage than the 194 used at the front side marker position.
Although both the 194 and 1816 share the miniature wedge base type and the same 12-volt operating voltage, their differing T-size designations indicate they are not interchangeable between front and rear positions.
Both bulbs conform to ANSI standards applicable in the United States and Canada, placing them within a widely distributed specification framework common to North American vehicle lighting.