The National Highway Traffic Safety Administration said the recall would begin in November.
The recall involves 2009-2010 Ram 1500 and Dodge Dakota trucks made between July 1, 2009 and Nov. 30, 2009.
The NHTSA said a loose rear axle pinion nut could result in a crash "with little warning," to the driver.
Chrysler said it would install a pinion nut retainer free of charge.
Consumers can call 888-327-4236 for information.