The International 7700 front turn signal requires a 3157NA bulb size while the rear turn signal uses a 3157 bulb size. The replacement chart covers vehicle production spanning 2005 to 2007.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The International 7700 uses the 3157NA for its front turn signal across the 2005-2007 model years.
The 3157NA is a dual-filament wedge bulb built to the T25 form factor, rated at 12V with a 27W high filament and a 7W low filament, and features natural amber glass.
The natural amber glass of the 3157NA produces an amber output directly from the bulb itself, without relying on a colored lens to achieve the required turn signal color.
The rear turn signal on the International 7700 for the same 2005-2007 model years takes the 3157 bulb.
The 3157 shares the same T25 wedge form factor, 12V operating voltage, and 27W/7W dual-filament configuration as the 3157NA, but its glass is clear rather than amber-tinted.
Both the 3157 and 3157NA conform to ANSI standards applicable in the United States and Canada.
Because the 3157 and 3157NA share the same physical T25 form factor and electrical ratings, they are mechanically interchangeable, but substituting a clear 3157 in place of the 3157NA in the front position would alter the color output unless the housing lens itself is amber.
The dual-filament design of both bulb types allows a single bulb to serve two lighting functions, with the higher 27W filament typically assigned to the turn signal or brake function and the lower 7W filament assigned to a running light function.