why does the back wheels of my silverado move to the side when im braking
the back wheels move to the side when im braking ps the back of the truck has airbags so there are no leaf springs
How hard are you braking? Check the axle seals to see if they are leaking on the the brake shoes and causing lockup, rear wheels locking up can cause them to slide side to side.
Unless I'm not understanding what you are describing?