The Peterbilt 325 front turn signal bulb size measures 3157NA or 2057, while the rear turn signal bulb size measures 1157 or 2057. The replacement chart covers vehicle production years spanning 2008 through 2015 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 325 front turn signal uses the 3157NA bulb for model years 2011-2015 and the 2057 bulb for 2008-2009.
The 3157NA is a dual-filament T25 wedge bulb rated at 12V with a high/low filament draw of 27W and 7W respectively, and features natural amber glass rather than a clear envelope.
The natural amber glass of the 3157NA produces a colored output without relying on an amber lens, which distinguishes it from clear variants of the same base type.
The Peterbilt 325 rear turn signal uses the 1157 bulb for 2011-2015 and the 2057 bulb for 2008-2009, meaning front and rear positions share the same bulb only in the 2008-2009 model years.
The 2057 and 1157 bulbs share the same BAY15d bayonet base, which is a dual-contact offset-pin base that physically allows one to substitute for the other in many housings.
Despite the shared base, the 2057 draws 26.9W on its high filament compared to the 1157's 21W, and 8W on its low filament compared to the 1157's 5W, making them electrically distinct.
All three bulb types listed across these specifications conform to ANSI standards applicable in both the United States and Canada.
All bulbs specified for the Peterbilt 325 turn signals operate on a 12V system and use dual-filament construction, where one filament serves the turn or brake function and the other serves a lower-intensity running light function.
The 3157NA uses a wedge-style base rather than a bayonet base, making it physically incompatible with the sockets used by the 1157 and 2057 despite sharing a similar dual-filament electrical configuration.
The front and rear turn signal positions on the 2011-2015 Peterbilt 325 require different bulb types, with the 3157NA at the front and the 1157 at the rear, so the two positions are not interchangeable for those years.