Kenworth T660 Turn Signal Bulb Size

Kenworth T660 front turn signal bulb uses a 4157NA size. The replacement chart covers 2008 to 2011 vehicle 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.

Front Turn Signal

Years	Bulb Size
2008-2011	4157NA

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament wedge bulb (T25), natural amber glass. 12V, 27W/7W.	4157NA

Other Locations

Additional Notes

The Kenworth T660 uses the 4157NA bulb for the front turn signal across the 2008-2011 model years.
The 4157NA is a dual-filament bulb, meaning it serves two brightness levels within a single unit. The higher-output filament operates at 27W, while the lower-output filament operates at 7W.
The 4157NA follows the ANSI standardization system, which is recognized across the United States and Canada, placing it within a widely distributed bulb category.
The bulb is housed in a T25 wedge form factor. A wedge base requires no separate metal socket pins, as the glass envelope itself acts as the retention mechanism when inserted into the housing.
The natural amber glass of the 4157NA produces its color through the glass coating rather than through a colored lens or housing, which is a relevant fitment consideration when replacing it with a clear-glass equivalent such as the 4157.
The 4157NA operates on a 12V electrical system, consistent with standard automotive voltage.
The "NA" suffix in the 4157NA designation specifically denotes the natural amber glass finish, distinguishing it from the otherwise electrically identical 4157. Substituting a non-amber variant may affect compliance with turn signal color regulations depending on the lens color of the housing.