As our ‘60s and ‘70s muscle cars age, they have lived well past whatever the engineers originally planned for these cars to survive. Specifically, with early Chevelles, we’ve learned the hard way to monitor stock lower control arms for cracks that occur near the ball joint area. 

In our case, we were in the midst of a front drum brake conversion when we noticed a crack in the right front lower control arm that was only about a 1/2-inch from the ball joint. Unchecked, this would have failed in a most spectacular way. This was on our ’66 Chevelle drag-test mule and we can only imagine the carnage if this had occurred at 120 mph in the traps at the end of the track. We immediately replaced both lower control arms with tubular aftermarket arms from Global West that are much stronger and infinitely safer.

This is what happens when the lower control arm cracks and eventually fails in the area around the pressed-in ball joint. Luckily, this failure occurred at a slow speed in a parking lot. If this had happened at 70 mph, the results would have been catastrophic.

The problem stems from the metal-to-metal contact that occurs when the steering arm stops hit the lower control arm. The stress of this constant contact causes a crack to form at the contact point on the control arm and then continue in the direction of the load that is concentrated at the lower ball joint. In the GM upper and lower control arm suspension with the coil spring located on the lower control arm, this arm carries all the weight of that corner of the car while the upper control arm is there mainly as a locating point.  

To underscore this situation, a friend purchased a ’66 El Camino with a 454ci big-block a few years later and suffered a right front lower control arm failure when the crack reached the ball joint and completely fractured the control arm. Luckily, he was exiting a parking lot when the failure occurred and was only moving about 5 miles per hour. Damage was limited to the broken lower control arm and shock absorber. With two replacement lower control arms installed and a fresh alignment, he was back on the road in a very short time. 

The inspection procedure is simple enough for any ’60s GM car that retains the original production lower control arms. This simply requires cleaning the area around the lower control arm ball joint area where the steering arm contacts the control arm. Clean the area and look for hairline cracks in the arm. If you find a crack, do not drive the car until the control arm is replaced. Even a small crack can completely fail very quickly and if the failure occurs at speed, the damage could be very severe with personal injury.