The Peterbilt 375 front and rear turn signal bulbs utilize 198 and 2057 sizes. A replacement chart documents bulb specifications across the 1987 to 1996 production range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 2057 bulb is the most frequently specified size across both the front and rear turn signal positions on the Peterbilt 375, appearing across model years 1987-1996 in both locations.
The 2057 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V and drawing 26.9W on its high filament and 8W on its low filament, making it suitable for combined turn signal and running light functions.
The 198 is a miniature wedge bulb of the T5 type, rated at 12V and 2W, representing a significantly lower power draw than the 2057.
Both the 198 and 2057 are ANSI-standardized bulbs recognized in the US and Canada, meaning they conform to defined performance and dimensional standards within those markets.
On the Peterbilt 375, the correct bulb size for both front and rear turn signals is conditional on the headlamp configuration present on the vehicle, meaning two trucks of the same model year may require different bulbs.
For the 1996 front turn signal, the standard fitment is the 198, while trucks equipped with Halogen Capsule Headlamps require the 2057, reversing the typical pattern seen in several other years.
The rear turn signal on the 1989 Peterbilt 375 follows the same reversal pattern as the 1996 front position: the base fitment is the 198, while the Halogen Capsule Headlamp variant calls for the 2057.
The 4 Round Headlamp configuration is cited as a conditional fitment factor exclusively in the front turn signal data for model years 1988-1992, consistently pairing that configuration with the 198 bulb.
The 4 Rectangular Headlamp configuration appears only in the 1988 front turn signal entry, where it is associated with the 2057 bulb rather than the 198.
Because the 198 and 2057 use different base types, a wedge base versus a BAY15d bayonet base, the two bulbs are not interchangeable regardless of voltage compatibility.