Ram 3500 Back Up Light Bulb Size

The Ram 3500 back up light utilizes 1156, 921, and 7440 bulb sizes depending on the specific vehicle configuration and lighting assembly. Available data for the specified components covers a range from 2011 through 2024.

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	US Type	EU Type	Shop
2023-2024	1156	P21W	Check Price
2019-2020	921 (With Halogen Capsule Headlamps)	W16W	Check Price
2019-2020	7440 (With LED Headlamps)	W21W	Check Price
2013-2018	7440 (With Projector-type Headlamps)	W21W	Check Price
2013-2018	921 (Without Projector-Type Headlamps)	W16W	Check Price
2011-2012	921	W16W	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156	Check Price
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W	Check Price
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921	Check Price
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440	Check Price

Other Locations

Additional Notes

The Ram 3500 backup light specifications reference three distinct bulb types across the 2011-2024 model years: the 1156, the 921, and the 7440. All three are ANSI-standardized bulbs rated for use in the United States and Canada, and all operate at 12 volts.
The 921 is a T15 wedge-base bulb rated at 16W, making it the lowest-wattage of the three types listed. It requires no locking mechanism beyond the wedge fit of its base, which seats directly into a compatible socket.
The 7440 is a T20 wedge-base bulb rated at 21W. Although it shares the wedge-base design of the 921, the two are not interchangeable due to differences in base size and wattage. Substituting one for the other risks improper fitment or electrical mismatch.
The 1156 differs from both wedge-type bulbs in its base design. It uses a BA15s bayonet base, which locks into the socket with a twist rather than a friction fit. It is also rated at 21W, matching the 7440 in wattage but incompatible with wedge-type sockets.
For the Ram 3500 model years 2013-2019, the correct backup light bulb depends on the headlamp configuration of the specific vehicle. Units equipped with projector-type or LED headlamps take a different backup bulb than those without those headlamp types, making headlamp configuration a required reference point before selecting a replacement.
The 2020 Ram 3500 follows a similar split, with the 921 applying to vehicles with halogen capsule headlamps and the 7440 applying to those with LED headlamps. This pairing of backup light fitment to headlamp type is a recurring pattern across multiple model years in these specifications.
The 2023-2024 Ram 3500 uses the 1156 with its BA15s bayonet base, representing a departure from the wedge-base bulbs used in earlier model years. This base type is not compatible with sockets designed for T15 or T20 wedge bulbs.
The 2011-2012 Ram 3500 specifies the 921 without any conditional fitment notes, indicating a single backup light bulb type applied across all configurations for those years.