Pontiac Trans Sport Back Up Light Bulb Size

Additional Notes

• The Pontiac Trans Sport uses two distinct back up light bulb types across its model years: the 2356 and the 3057, both of which are ANSI-standardized bulbs rated for use in the United States and Canada.
• The 3057 is a dual-filament wedge bulb in the T25 form factor, operating at 12 volts with a 27W/7W power rating across its two filaments.
• The 2356 is a dual-filament bulb fitted with a BAY15d bayonet base, operating at 12 volts.
• The BAY15d base on the 2356 and the wedge base on the 3057 are physically incompatible mounting types, meaning the two bulbs are not interchangeable despite both being dual-filament 12V designs.
• The 3057 applies to the Pontiac Trans Sport for model years 1990-1996, representing the longer-running fitment across the vehicle's production span covered in these specifications.
• The 2356 applies to the 1997-1998 model years, reflecting a change in the specified back up light bulb type relative to earlier production years.
• A dual-filament bulb contains two separate wire filaments within a single envelope, each serving a distinct circuit function, which is a common design in automotive rear lighting applications.
• The T25 designation on the 3057 refers to the wedge base size classification, where the number indicates the bulb body width in millimeters, placing it in a mid-range wedge category used across various automotive lighting positions.