In late 1959, the introduction of General Motors' new body style for its line of trucks marked the most extensively changed trucks in its entire history. Beyond the obvious radical departure in styling from the '55-59 Chevrolet and GMC light-duty trucks, the '60 Chevrolets unveiled underpinnings unlike anything ever seen before. Up front, the truck's transformation earned a place in history as the first light-duty trucks to feature independent front suspension. In the rear, GMC retained the parallel leaf spring arrangement from previous years, but Chevrolet opted for a two-link setup known as trailing arm, or truck-arm, that utilized coil springs instead of leaf. Focusing on the rear suspension, GMC retained parallel leaf, because leaf springs were believed to behave better under a heavy load, satisfying GMC's desire to be known as a heavy-duty truck. Interestingly though if a GMC buyer wanted to special order a coil-spring rear suspension, or a Chevrolet buyer desired leaf springs it was within the realm of possibilities.

Just as the '57 Chevy passenger car switched from rear leaf springs in its model year to the debut of the '58 Chevrolet with coil springs the reasoning was to improve ride quality. For anyone that has ever owned both brands of truck there is no doubt the Chevrolet rides better.

The factory design of the Chevy's trailing arm is an I-beam configuration obtained by joining two stamped-steel C-channels back-to-back to form the beam. If the stock Chevy trailing arm is never subjected to rust or impacted it will live forever. In the case of our '66 Chevy C10, one of the trailing arms was severely bent, probably caused by many years of off-road use and abuse in its California high-desert home. We didn't discover any structural damage from rust on our T-arms, but we have seen stock trailing arms from the rustbelt rendered dangerous from exposure. The trialing arms we selected to replace the stock units on our '66 came from Early Classic Enterprises, located in Fresno, California. Playing the devil's advocate we called Early Classic, and asked why anyone would want to install their trailing arms on a '60-72 Chevrolet or GMC truck. After explaining the practical advantages of Early Classic's trailing arms, Stan told us that a lot people buy their trailing arms because as a custom fabricated part, they look a lot better than stock ones. Getting back to practical advantages, Stan explained that as a sealed unit, Early Classic's trailing arms cannot fill up with water and rust from the inside. Additionally, Stan claimed the rectangular design of their trailing arms is three times stronger than a tubular trailing arm constructed with the exact same wall thickness of steel. Although we didn't use it, Early Classic manufactures a really clean looking crossmember that can be used in conjunction with their trailing arms. The Early Classic Enterprises' crossmember can also be used to convert GMC trucks from leaf to coil springs. Another point Stan made for choosing coil springs over leaf springs is coils can be ordered in heights that range up or down in 1-inch increments from stock, and are more adjustable than leaf-springs. In order to raise or lower leaf springs different shackle configurations or leaf packs must be used.

After we got off the phone with Stan it occurred to us that trailing arms are the easiest type of rear suspension to convert to air-ride just by installing airbags in place of the stock coil springs. It is fine if a person doesn't mind having to deal with an air-compressor, valves, switches, plus a whole bunch of hoses, and wiring.