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.
Early Classic Enterprises'...
Early Classic Enterprises' trailing arm kit is available for '60-72 Chevrolet and GMC trucks. It is important to note there are three variations that are broken into year models. The first kit fits '60-62 trucks, the second kit fits '63-64, and the third kit fits '65-72 year models.
Here's a worm's eye view of...
Here's a worm's eye view of a stock Chevrolet trailing arm rear suspension in place. Typically, the stock Chevy trailing arms found on trucks from the rustbelt will be heavily rusted at the long seam running down the center of the two C-channels that form the I-beam.
Bent trailing arms such as...
Bent trailing arms such as this one can affect rear wheel alignment or ride height if the damage is severe enough.
The '66 Chevy pictured here...
The '66 Chevy pictured here was built in San Jose, CA and has been here for its entire life. Nevertheless, a cheater bar was necessary to undo some of the bolts retaining the suspension.
Since Early Classic's kit...
Since Early Classic's kit comes with all of the necessary replacement hardware and every original bolt was frozen (rusted) tight, Steve cut the U-bolts retaining the rearend with a 4-inch cutting disc on a die-grinder.
The bolts attaching the coil...
The bolts attaching the coil springs to the trailing arms were cut with a die-grinder as well. Since we weren't replacing the coil springs the top mounting bolts were left alone.
Installing Early Classic Enterprises trailing arm kit was a breeze; it was removing all the rusty old parts from the Chevy that was a real bear. There's two ways to go about removing the stock trailing arms. If a person doesn't have access to a hoist and has to rely on a floor jack and jack stands the first step is to remove the bed and then raise the rear end of the truck into the air as high as possible to gain access. We chose to raise the Chevy on a hoist, and work from underneath, which is by far the easiest way to do the job. Not having a hoist at home we put in a quick call to Kevin and Steve at KA Custom in Huntington Beach, California, and asked if they wouldn't mind revealing some tricks-of-the-trade we could reveal to our readers who like to do the work themselves.
Our '66 C10 was the truck...
Our '66 C10 was the truck Classic Chevy 5-Speed used to prototype its '60-72 Chevy C10 TKO 5-speed conversion - After 12,000 miles of power-shifting, burnouts, and general abuse the Tremec still looks as good as the day it went in, and better yet, still works.
The emergency brake cables...
The emergency brake cables had to be disconnected from the old trailing arms, and reattached to the new Early Classic trailing arms by first releasing the e-brake cable from the J-hook on the frame to provide slack.
Steve used needle-nose pliers...
Steve used needle-nose pliers to pull this clip in order to remove the e-brake cables from the stock trailing arms. For installation onto the Early Classic trailing arms the process was reversed.
The trailing arms are attached...
The trailing arms are attached with a bolt that passes through a mounting bracket located on the crossmember.
The Early Classic trailing...
The Early Classic trailing arm fell easily into place on the driver side by pushing it forward. This was because there was no damage to the original mounting point.
On the passenger side there...
On the passenger side there was damage existing to the trailing arm mounting bracket, so Steve used a crescent wrench to spread the bracket apart enough to push the Early Classic trailing arm into place.
A come along was used to pull...
A come along was used to pull the rearend forward, and align the mounting holes on the lower shock bracket enough to drop the new U-bolts into place.
Using the new mounting hardware...
Using the new mounting hardware supplied with the Early Classic trailing arms, Steve bolted the stock coil spring onto the new trailing arm (also a pickup point for airbags).
Steve pulled the e-brake cable...
Steve pulled the e-brake cable forward enough to allow the cable to pass through the slot on the Early Classic trailing arm.
The finishing touch for the...
The finishing touch for the driver side trailing arm was to reattach the shock absorber, and tighten the nut on the lower bracket.
Not assuming the passenger...
Not assuming the passenger side would be the same story as the driver's, Steve discovered the U-bolts would unbolt instead of having to be cut, which would have consumed more time.
The time gained on the right...
The time gained on the right side U-bolts was lost to having to repair, and fit the trailing arm. Steve used a ball-peen hammer to compress the bushing narrower.
A mallet was used to help...
A mallet was used to help drive the Early Classic trailing arm into the mounting bracket on the crossmember.
To align the hole to install...
To align the hole to install the mounting bolt through the mounting bracket a pin punch was wiggled-in.
This allowed the mounting...
This allowed the mounting bolt to easily slide through and tighten down.
Things moved fast once both...
Things moved fast once both of the Early Classic trailing arms were connected to the crossmember. After pulling everything into alignment, Steve buzzed the U-bolt down with an impact wrench.
The finishing touch was to...
The finishing touch was to tighten down the lower shock absorber.
From start to finish, including...
From start to finish, including all of the time that was needed to cut off rusted bolts and parts it took Steve less than two hours to install the Early Classic Enterprises trailing arm kit.