Plymouth GTX Back Up Light Bulb Size

The Plymouth GTX back up light requires 1156, 1073, or P21W bulb sizes depending on the specific version of the vehicle. Available data covers the period from 1967 through 1971.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1969-1971	1156
1968	1073
1967	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073

Other Locations

Additional Notes

The 1156 bulb is the most frequently specified backup light bulb across the Plymouth GTX model years covered, appearing in 1967 and 1969-1971.
The 1156 is an ANSI-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The BA15s bayonet base uses a single contact pin, which locks the bulb into its socket with a push-and-twist motion.
The Plymouth GTX (1968) uses the 1073 bulb rather than the 1156 for its backup lights.
The 1073 shares the same 12V operating voltage and BA15s bayonet base as the 1156 but draws only 13W, making it a lower-wattage variant.
Because the 1073 and 1156 share the same BA15s base, the two bulbs are physically interchangeable in terms of socket fit, though their wattage ratings differ.
Substituting a 1156 in a socket designed for a 1073 would introduce a higher current draw than the original specification for the 1968 model year.