2007 Dodge Ram 1500 4x4 , hammer sound ftom rear , stop back up and go it’s fin

Hello, I would recommend stopping and not driving until you check the braking system thoroughly. Also check suspension components. This isn't normal and could compromise your safety. Can't speculate on what could cause the noise as we can't hear it online, but it is consistent with concerns that could cause safety issues. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops