There are two reasons so many trucks throughout the years were designed with a traditional parallel leaf spring rear suspension: It's simple and cheap. It works really well from a manufacturing and utilitarian standpoint and has stood the test of time throughout the life of the automobile, but what if you get tired of being treated like dice in a Yatzee cup?
Cheap and simple don't usually add up to a good ride, and unless you're carrying a load in your truck, it rides, well, like a truck. GM used a trailing arm and coil spring rear suspension setup on light-duty trucks from '67-72, but switched back to parallel leaves in '73, most likely due to cost. If you have driven a truck with trailing arms, it's obvious there's something missing: the rough ride. Classic Performance Products, aka CPP, has been offering owners of stock trailing arm-equipped Chevy and GMC trucks their upgraded tubular version of GM's original trailing arm design for a few years now and just finished a kit to convert the other '63-87 1/2-ton shortbed GM trucks with parallel leaf springs to well-mannered trailing arms.
One of the biggest drawbacks to a parallel leaf setup is the amount of lateral or side-to-side slop they allow. Like a four-link setup, trailing arms utilize a Panhard bar (Trac Bar) to keep the rearend from moving laterally and should do so as long as they're installed properly. Another disadvantage to leaf springs is spring wrap both under acceleration and deceleration, which puts quite a bit of stress on the drivetrain and suspension. Trailing arms are much like ladder bars, which have been used in drag racing and street rods for many years and help keep the power to the ground where it belongs and the pinion pointing where it should. Also, thanks to the coil springs used with trailing arms, it is easy to adjust or totally change the ride height in the rear end without the hassle of messing with leaf springs. CPP has six different coil spring heights as well as three lowering blocks available to use with a stock truck or any one of their trailing arm kits.
CPP put together their Chevy Trailing Arm Conversion kit using their tried-and-true, TIG-welded, quarter-inch-wall DOM tubular trailing arms; CNC-bent, TIG-welded, quarter-inch steel trailing arm crossmember; C-notch/frame reinforcement sections; adjustable Trac Bar; shocks; coil springs; and all necessary heavy-duty Grade 8 fine-thread hardware. The kit isn't for the novice-most major chassis alterations aren't. But with that being said, all the welding is done on the rear axle housing and not on the truck's frame, so a novice could do much of the work and finish with help from a skilled friend or shop. As always, CPP has knowledgeable people answering their tech line who happen to be in the same building where the kit was designed and built should you have any questions.
Our subject for this install is a smog-equipped '79 Chevy Heavy Half shortbed pickup that rode like a buckboard despite being a clean original truck. After the swap it sailed smoothly down our rough, overcrowded roads. The difference in the truck's ride is like night and day with the CPP Trailing Arm Conversion compared to the stock parallel leaf springs. From crossing the first set of railroad tracks leaving The Muffler Man to jumping on the freeway, the '79 won't be rattling anyone else's fillings out. Follow along and see what your kidneys could soon be thanking you for.
Here's the meat and potatoes of CPP's new Trailing Arm Conversion kit for '63-87 Chevy and
One of the first things you need to do to start disassembling the stock parallel leaf spri
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