As fond as we are of our classic Mustangs, they came with their share of annoying and sometimes dangerous engineering flaws, such as leaking cowl vents, seatbacks that broke, braking system defects, defroster air doors that fell apart, parking brake mechanisms that never worked well, door latches that froze in the wintertime, and shock towers that cracked. Cracked shock towers are not only hard on front-end alignment, but also dangerous because a crack can turn into catastrophic shock tower and steering system failure.
To understand why shock towers crack, you have to know a little about Mustang suspension systems. Classic '65-'73 Mustangs have a coilover upper control arm front suspension system. So did those first '62-'65 Chevy II compacts before GM switched to a bolt-on front subframe system with conventional control arms. Although the Mustang's front suspension system was an economical approach, it was not a good design in terms of longevity, reliability, and handling. It also had one other inherent flaw-upper control arm binding and unwanted slack. When upper control arms bind, the shock towers flex with suspension articulation, causing metal fatigue and cracking.
In all the years we've been writing about classic Mustangs, we've never seen cracking on '65-'66 or '71-'73 Mustangs, only '67-'70s. And that's what we're addressing here-a '70 SportsRoof belonging to Tim Love of Southern California. Tim's Mustang suffered from front-end alignment woes, sloppy handling, and suspension noise. When Tim investigated the nature of these problems, he found a badly cracked lefthand shock tower on the verge of failure. That's when he pulled the 351W engine for an even closer look and called Mustangs Plus for solutions. They decided to replace both shock towers.