The Peterbilt 379 front and rear turn signal bulbs utilize a 2057 or 198 size specification for replacement applications. The replacement chart covers vehicle production spanning 1986 to 2007 with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 2057 is the dominant bulb type across the Peterbilt 379 turn signal specifications, appearing in both front and rear positions across the full 1986-2007 model year range covered.
The 2057 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments drawing 26.9W and 8W respectively, and it is classified as a brighter variant of the 1157 under the ANSI standard used in the US and Canada.
The 198 is a miniature wedge bulb of the T5 type, rated at 12V and 2W, and is also an ANSI-standard part used in the US and Canada. Its single-filament, low-wattage design contrasts sharply with the dual-filament 2057.
On the Peterbilt 379, the 198 bulb is a conditional fitment, appearing only in conjunction with specific headlamp configurations rather than as a universal replacement across all trims.
For the 1998-2007 model years, both front and rear turn signals use the 2057 exclusively, with no conditional variants listed for those positions.
In the 1986-1997 range, multiple model years carry two separate front turn signal entries, meaning the correct bulb depends on which headlamp configuration is installed on that specific vehicle.
The 4 rectangular headlamp configuration is associated with the 198 bulb in the front turn signal position across several years, including 1986, 1990, 1992, 1995, 1996, and 1997.
The halogen capsule headlamp configuration triggers a 198 fitment in both front and rear positions depending on the year, as seen in entries for 1987-1989, 1992-1993, and 1997.
The 4 round headlamp configuration is linked to the 198 bulb in specific years, appearing in the front turn signal for 1989 and in the rear turn signal for 1987 and 1990.
Because the 2057 and 198 are not interchangeable, wattage and base type being entirely different, the headlamp configuration present on a given 379 is a necessary reference point before selecting a turn signal bulb for affected model years.