TeraFlex Dana 60 HD Ball Joints replace the weak factory ball joints that are unable to handle the demands of repeated off road use or larger tires. The ball joint studs are made from 4140 chrome moly steel for high hardenability and are heat treated to provide excellent fatigue and abrasion resistance. The weak factory plastic cups have been eliminated. The upper ball joint has two sintered metal bearings to handle the rotational load and the lower ball stud rides in a metal cup that is threaded to provide for a precise pre-load. In-between the lower ball joint threaded cup and ball stud is a special plate spring made from high carbon tool steel for excellent wear resistance as the lower joint must bear the vehicle weight. The lower ball joint also features an oversized flanged nut for a good bearing surface against the outer knuckle. Both ball joints have grease zerks that are easy to service. The lower ball joint has a special flush needle zerk that is offset for u-joint clearance and ease of maintenance. Note: We recommend ball joints without knurls as they will not score the inner knuckle and open up the bore. We also offer ball joint with knurls for ball joints that have a loose press fit in the inner knuckle due to repeated ball joint replacement or if knurled ball joints have been installed in the past.