Mustang GT Convertible 2007 with clunking noise in front end

ford
mustang

#1

When I drive over bumps I hear a clunking noise which sounds like something loose is banging around under the front end. When I jack it up and inspect I cannot find anything loose. The dealer says that I need new ball joints but I only have 72,000 miles on it. The dealer demonstrates the need for new ball joints by putting it on the lift and pushing & pulling on the front & back of the tire and it moves at the ball joint. I believe it moves because he is moving the entire steering linkage and of course it is going to have some play. When I ask him to push & pull on the top & bottom of the tire or just push up on the bottom of the tire there is no movement. Should I believe the dealer or is he just trying to make an $800 boat payment?