The recall involves RAV4 SUVs manufactured from 2006 to 2011 and 2010 Lexus HS 250h sedans in the U.S.
The company says if rear suspension nuts aren't tightened properly after a wheel alignment, the arms can rust and separate from the vehicle.
Toyota has reported nine crashes and three minor injuries from the problem.
The National Highway Traffic Safety Administration opened an investigation into the problem in June after getting several reports from drivers, including one who reported swerving over four lanes of an interstate when the suspension arm disconnected. Four drivers told NHTSA they temporarily lost control of their vehicles because of the issue.
Toyota says it will notify owners by mail when it's time to take them to dealers for a free repair. In the meantime, drivers were advised to contact their dealers if they hear an abnormal sound in the rear of the vehicle.
It's the latest issue for the popular RAV4, which is currently involved in a government investigation of door fires that have been linked to power window switches.
The Associated Press contributed to this report.