Pontiac Trans Sport front turn signal bulbs use 3157NA or 3057NA size, while rear turn signal bulbs use 3156, 2456, or 2057 size. The replacement chart covers 1990 to 1998 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.
The Pontiac Trans Sport front turn signal uses the 3157NA bulb for model years 1994-1998 and the 3057NA for 1991-1993. Both are dual-filament T25 wedge bulbs rated at 12V with a 27W high filament and 7W low filament, and both feature natural amber glass rather than a clear envelope.
The natural amber glass on the 3157NA and 3057NA eliminates the need for an amber-tinted lens to produce the legally required amber turn signal color, as the tint is built directly into the bulb.
Although the 3157NA and 3057NA share the same T25 wedge base, voltage rating, and wattage, they are distinct ANSI part numbers and are not universally interchangeable across all vehicle applications. The Trans Sport specifications list them for separate model year ranges on the front position.
The rear turn signal on the Pontiac Trans Sport uses five different bulb types across the 1990-1998 model years, reflecting a notably varied fitment history for a single lamp position on one model line.
The 2057 bulb, specified for the rear turn signal on the 1990-1996 Trans Sport, uses a BAY15d bayonet base and is described as a brighter variant of the 1157. Its dual-filament design at 12V draws approximately 26.9W on the high filament and 8W on the low filament, making it suitable for combined turn signal and running light functions.
The 1997 rear turn signal specifies the 2456, a festoon-style bulb rated at 12V. Festoon bulbs use a cylindrical form factor with end-cap contacts rather than a base, which means it is physically incompatible with the bayonet or wedge sockets used by the other bulb types listed in these specifications.
The 1998 rear turn signal specifies the 3156, a single-filament T25 wedge bulb rated at 12V and 27W. Unlike the 2057 used in earlier model years, the 3156 carries only one filament, indicating the 1998 rear turn signal circuit does not share the bulb with a running light function in the same socket.
The T25 wedge base is shared by the 3157NA, 3057NA, and 3156 bulbs, but the single-filament 3156 and the dual-filament 3157NA are not interchangeable. Installing a single-filament bulb in a socket wired for dual-filament operation would result in the loss of one lighting function.
All bulb types listed across both the front and rear turn signal positions conform to ANSI standards applicable in both the United States and Canada, indicating regulatory compliance for North American market vehicles.
The 2057 and 3157NA both operate at 12V with a high-filament draw near 27W, but they use entirely different base types, the BAY15d bayonet and the T25 wedge respectively, making them physically non-interchangeable despite the similar wattage.