International 8600 TranStar Turn Signal Bulb Size

Additional Notes

• The International 8600 TranStar uses the 3157NA bulb for the front turn signal across all listed model years from 2008-2018.
• The 3157NA is an ANSI-standardized bulb, meaning it conforms to a defined specification recognized across the United States and Canada.
• The 3157NA is a dual-filament bulb, operating at 27 watts on the high filament and 7 watts on the low filament, which allows it to serve both turn signal and parking light functions within a single housing.
• The bulb operates on a 12-volt electrical system, consistent with standard automotive and commercial truck electrical architecture.
• The T25 designation refers to the wedge-style base of the bulb, a physical format that must be matched precisely to the socket in the vehicle's housing for proper fitment.
• The "NA" suffix in 3157NA indicates natural amber glass, meaning the amber color is produced by the glass envelope itself rather than by an amber-coated lens or housing.
• Because the amber tint is built into the glass, substituting a clear 3157 bulb in place of the 3157NA would alter the color output of the front turn signal on the International 8600 TranStar.
• The 3157 bulb family includes several variants that share the same T25 wedge base, but differences in glass color and filament wattage ratings mean not all variants are interchangeable without affecting light output or compliance.