Ram 2500 Back Up Light Bulb Size

Additional Notes

• The three bulb types specified across the Ram 2500 backup light positions are the 7440, 1156, and 921, all of which conform to ANSI standards recognized in the United States and Canada.
• The 7440 and 1156 share the same 12V, 21W electrical rating, while the 921 operates at a lower 16W output on the same 12V supply, making the 921 the least powerful of the three types listed.
• The 7440 uses a T20 wedge base and the 921 uses a T15 wedge base; although both are wedge-type bulbs, their physical sizes differ and they are not interchangeable with each other.
• The 1156 uses a BA15s bayonet base rather than a wedge base, which means it is mechanically incompatible with sockets designed for either the 7440 or the 921 regardless of the shared wattage with the 7440.
• For the Ram 2500 in model years 2013-2018, the correct backup light bulb depends on headlamp configuration: projector-type headlamps correspond to the 7440, while non-projector configurations correspond to the 921.
• The same headlamp-based split applies to the 2019-2020 model years, where LED headlamp-equipped vehicles use the 7440 and those with halogen capsule headlamps use the 921.
• The 2011-2012 model years specify the 921 without any conditional trim or equipment qualifiers, indicating a single fitment for those years.
• The 2023 model year is the only year in the specifications that calls for the 1156, while the 2024 model year returns to the 7440, making the bayonet-base 1156 specific to that single year in this dataset.