A clamp assembly for a hydroforming die includes a stationary lower bed to support a lower die half of the hydroforming die, a stationary upper bed spaced above the lower bed, at least one guide post extending between the lower bed and the upper bed, a movable slide disposed between the upper bed and the lower bed and movable along the at least one guide post to support an upper die half of the hydroforming die, a lifting cylinder operatively connected to the movable slide to move the movable slide and upper die half toward and away relative to the lower die half, at least one link mechanism connected to the upper bed and the movable slide to equalize a force on the hydroforming die, and at least one linkage cylinder operatively connected to the at least one link mechanism to activate the at least one link mechanism to prevent the movable slide and upper die half from moving away from the lower die half to keep the hydroforming die closed during a hydroforming process.