How to Install Rear Trailing Arms - 1967 Chevelle
One of the things that makes product management so much fun is being able to find and fill needs in the market. When you are part of that market, all the better! Right about the time that I bought the Chevelle we learned, from some heat-mapping data gathered on our muscle car shop pages. The biggest take away was that A-Body GM was one of the hottest, and at that time, most underserved markets we sold in.
Challenge accepted. In addition to adding tens of thousands of muscle car specific skus through the acquisition and expansion of Camaros & Classics in 2015, I made it my personal mission to give those muscle car customers what they came for.
One of the first in-house projects I initiated along this line was to build a high-quality rear trailing arm kit for 64-72 Chevelle that utilized a really trick forged rod end that was presented by one of our manufacturing partners. The A-body rear suspension has a quite unique set of requirements. If you want to eliminate wheel hop and promote “forward bite” the bushings need to be very stiff. However, when the suspension goes through a cornering motion the bushing needs to comply in order for the triangulated four bar design to move through its range of motion. In most cases, a high durometer polyurethane bushing is used and the arms bind their way through the typical driving motion. Eventually, this takes its toll on the stamped sheet metal pivot mounts in the vehicle and they will tear. Roll control should be done by the sway bar. Not by binding the suspension links.
The proprietary Giro™ Technology engineered into these new pivots allows articulation while providing very firm front-to-back support during acceleration. This is accomplished by a variable depth in the bushing material itself. It’s wider at the front and rear and diminishes in thickness and durometer at the top and bottom. The steel insert sleeve that the bolt fastens through floats inside the self-lubricating bushing material. This creates a friction-free range of motion and silent operation.
The other thing I wanted to add to our rear trailing arm kit was extra value. We include all hardware, a heavy 30mm sway bar, and front mount braces. Powder coated gloss black, all for one price.
The process began with taking baseline measurements from original, stock trailing arms. The averages from 3 sets were used to determine baseline dimensions. From there, prototype samples were created. Those prototypes were test-fit on several vehicles for bolt-on. 64-72 use the same lower arms and sway bar, but the other components are generation-specific for 64-67 and 68-72.
While still tweaking these arms, my personal project took a turn toward the more extreme and I built the narrowed 9” for it. That gave the perfect opportunity to test in yet another environment. Knowing that the car would likely be extremely low with very tight tire fitment, I set out to find the limitations of these new components.
I found that when I put the suspension at full compression with the new housing, the clamshell portion of the trailing arm contacted the ear on the rear end. I remedied this by making a crescent-shaped relief in the front of the tab. This allowed the housing to travel up into the car far enough to contact the floor. Far further than it would ever go in actual application.
After having several chances to perfect the method for installing these arms I found two ways that proved to be clear winners. Depending on whether or not you were leaving the housing in the car will define your path. When retaining the rear end, I found it worked best to change just one link at a time while supporting the housing with a jack. You’ll find that a ratchet strap and long drift punch will aid any accidental movement or misalignment.
If you’re starting with an empty chassis, hang the lower arms under the car with the front pivot bolts and then put the housing on those and lift into place balanced on a jack. Install the upper arms with the adjusters loose and turned all the way in.
Speaking of the adjusters on the upper arms. These are so you can fine-tune your pinion angle and also make adjustments to how well center the housing is in your car. As I said before, my wheel and tire fit are very critical. These let allowed me to perfectly center the housing in the frame/body.
Once all four arms are attached, you can install your springs & shocks or coil-overs. Then you can hang the specially designed sway bar on the lower arm tabs to complete the installation. This bar is unique in that it does not intrude on ground clearance like the factory design.
In the next article, I’ll cover installing the coil-overs seen in some of these shots.