What makes classic Mustang shock towers crack and fail?  Important insight into a potentially dangerous situation. 

For more than 35 years of messing with classic Mustangs, we've seen our share of engineering issues and factory blunders.  That's an integral part of a classic Mustang's charm.  They aren't perfect and were never meant to be.  We love them unconditionally flaws and all.

When we think of engineering flaws and other things we love to hate about classic Mustangs, the front suspension and body structure are two of those things.  Squeaky upper control arm bushings and cracked shock towers on 1967-70 Mustangs just seem to go together and here's why.  Because upper control arm shafts and bushings are a threaded together assembly, there has always been a lot of friction going on there.  In fact, when these cars rolled off three assembly lines from sea to shining sea, they were cursed with dry upper control arm shafts and bushings.  And to add insult to injury, very few auto repair shops and Ford dealers knew what to do about them.  Some actually believed all they needed was a shot of penetrating oil to get rid of the squeak.  

Some shops cut holes in the shock towers to gain access to plugs that should have instead been grease jerks, not realizing you could screw in a 90-degree fitting and pump chassis lube in there all day long.  A whole lot of Mustang owners just turned up the radio to drown the squeak out.

As upper control arm bushings and shafts became dry over time, they began to bind, causing the shock towers to "oil can" or bend/flex with upper control arm movement.  You don't have to be a structural engineer to understand what this did to 1967-70 Mustang shock towers.  They cracked and even broke causing structural failure.  Although we've seen this problem a lot with 1967-70 Mustangs, we haven't seen it to any degree with 1965-66 or 1971-73.

The fix for this is, of course, shock tower replacement, which calls for engine removal to gain access.  Once the engine is out, shock tower replacement isn't all that hard.  Dynacorn makes complete shock tower assemblies made of a heavier gauge steel for 1967-70 Mustangs.  And while you're at it, make sure upper control arm bushings have 90-degree grease jerks for regular preventative maintenance.  They get a shot of grease at every oil change.