Steve Baur
Former Editor, Modified Mustangs & Fords
August 30, 2013

It's been quite a while since we covered the installation of Total Cost Involved Engineering's (TCI Engineering) modular independent front suspension on our 1966 Mustang fastback project, Colt of Personality, and we're finally addressing the rear suspension of our Coyote-powered Pro Touring machine with the installation of the company's torque arm rear suspension.

While the Mustang's original leaf spring suspension did a sufficient job at the time the cars rolled off the assembly line, there have been numerous improvements in suspension design, and a number of manufacturers that have engineered these designs to fit numerous classic cars. TCI Engineering now offers several suspension upgrade options, including a torque arm rear suspension for '64-'70 Mustangs, and '67-'68 Mercury Cougars.

The Torque Arm Design

One of the most prevalent designs at the time, the leaf spring suspension in the Mustang was used on a great number of vehicles—many fullsize trucks still use it—and provided a cost-effective solution to adequate handling. Much like the inexpensive four-link that replaced it, the leaf spring suspension is not well suited to hard cornering, and can often bind up. With the four-link, the upper control arms (which do a poor job of controlling both axle windup and lateral movement) tend to bind at the limit, which can lead to snap oversteer. It's still a step up from the leaf spring design, however, and can offer a great number of improvements to the classic Mustang/Ford enthusiast.

For a car built for the purpose of going fast wherever and whenever, the torque arm is a superior design that takes the upper control arms or leaf springs out of the picture altogether, and adds a Panhard bar to laterally locate the rearend. As it is fixed to the rearend housing, the torque arm greatly reduces axle windup and pinion angle changes, resulting in greater traction all around. You'll notice this in inclement weather, as well as when powering out of a corner, which you'll be able to do sooner and with your throttle than before.

Making horsepower is extremely easy these days, and a torque arm suspension will simply put it to the ground more effectively. You can find more information about the four-link and torque arm suspensions on TCI Engineering's website located in the Source box, and you can also find them on Facebook as well. TCI Engineering does a superb job of detailing the torque arm suspension installation in its 19-page instruction manual, so rather than duplicating that here, we'll give you the quick details regarding the install on our particular Mustang.

As it is fixed to the rearend housing, the torque arm greatly reduces axle windup and pinion angle changes

When installing the TCI Engineering suspension at the front of the Mustang last year, we encountered a number of rust issues that required repair before proceeding with the install. Such was the case at the rear as well, where rust was found perforating the torque boxes, and a previous attempt at floor repair was just as undesirable. With the new suspension, we're adding strength and we need to make sure that the foundation we are bolting the parts to is just as solid.

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