International S2554 front turn signal bulbs use 1156 size while rear turn signal bulbs use 1157 size. The replacement chart covers vehicle production spanning 1981 to 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The International S2554 uses the 1156 bulb for the front turn signal across all model years from 1981-1989.
The 1156 is a single-filament bulb operating at 12V and 21W, fitted with a BA15s bayonet base, and is recognized under ANSI standards in the US and Canada.
The BA15s base designation indicates a single-contact bayonet mount with a 15mm base width, which is not interchangeable with dual-contact bayonet bases.
The rear turn signal on the International S2554 uses the 1157 bulb across all model years from 1981-1989.
The 1157 is a dual-filament bulb rated at 12V with two wattage outputs, 21W for the turn signal filament and 5W for the secondary filament, and is also an ANSI-recognized standard in the US and Canada.
The 1157 uses a BAY15d bayonet base, which features two contacts offset at different heights to prevent incorrect installation, distinguishing it from the single-contact BA15s base used by the 1156.
Because the 1156 and 1157 share a similar physical profile but differ in base contact configuration, the two bulb types are not interchangeable despite their visual resemblance.
The dual-filament design of the 1157 allows the rear turn signal housing to serve more than one lighting function through a single bulb socket.