Generally the joint boots split, let water and dirt in which grinds the nylon "buckets" to dust. Or it simply wears the nylon over the years. Jack the car up by the lower arm until the tire is a couple inchs off the ground, take a long bar and lift the tire while watching the joint for up and down movement, more that a 1/8"? Time to consider replacement. Also take a smaller bar and check for lateral deflection while the lower arm is still loaded. 140's are MUCH more inclined to hammer out the caster bushings than lower joints, pretty much every one I've seen with bad lower joints also had the old haunted house creak when bounced. Upper joints will do the same along, these are replaced with the updated upper arm in pairs.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.