Actually it's a pretty good design and was used for many years. However things do wear out. More than likely the bushings and possibly the shafts are worn out. Another possibility is damage to the A arm itself from an accident. It's hard to notice that type of damage unless it's obvious. A lot of stuff happens over the years. Complete A arms, shafts, and bushings are available through a variety of aftermarket suppliers.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine