Use a level and tape measure to measure the desired ride height for the car. You are looking for about 8 inches of space between the axle centerline and the top of the wheel arch. Both sides need to match. This helps determine the correct width and clearance for the new rear-end housing.
Two types of suspension can be found up front: leaf or IFS. You can certainly swap the front housing for either one, but the 10-bolt version was only used in leaf spring trucks.
Just as with the rear leaf design, the front leaf in trucks is oversprung, so it’s easy to add clearance with a block lift. At the place where the axles come out of the ends, steering knuckles on the front housing connect to the wheel hub though a U-joint. The axle itself has a yoke on the end that holds one side of the U-joint, and the wheel hub connects to the other. This allows the steering knuckle to articulate. Newer four-wheel-drive trucks use constant velocity (CV) joints instead for longer life.
The 8.5-inch 10-bolt front axles were used from 1977 through 1991. When the GM 8.25-inch differential was introduced, the company used a completely different independent front suspension design. GM trucks with IFS use a design that is not similar to the 10- and 12-bolt differential.
Advanced Suspension Components
On classic GM cars and trucks, the rear suspension cradles the Chevy 10- or 12-bolt axle assembly and therefore, it plays a pivotal role in application of power to the ground as do the components inside the housing itself. To restore the original ride and handling, you can simply replace the stock bushings with rubber or poly-graphite bushings. But vintage muscle cars have antiquated handling and suspension performance. Even some modern compact cars can corner better than most of our preferred classic muscle. If you want to carve corners and put more power to the ground, a more substantial change is necessary. Many aftermarket companies offer suspension solutions, including Heigts, Chassisworks, Art Morrison, and Detroit Speed for classic GM rear-wheel-drive cars.
Global West Systems
Global West offers two lines of advanced suspension components: the Negative Roll and G-Plus. The Negative Roll system is the more advanced of the two. It requires tall spindles and delivers superior performance. But it is designed for road race applications and can be a little harsh on the street.
For most street-driven applications, the G-Plus system is the better option, offering performance and versatility in one complete kit. The G-Plus system can be used with stock, 2-inch-drop, or ATS spindles. It also works with most stock-style spindles, so almost any braking system can be used. I opted for a Global West system for the Buick. This kit includes the choice of using coil springs or coil-over shocks. Although the Global West coil springs are certainly capable of a quality ride,
I opted for the adjustability and control of the coil-over shocks. Global West uses QA-1 shocks with coil-over springs exclusively. Many consider these to be the best in the industry. I selected the double-adjustable shocks, which have 24 settings each for rebound and compression. These shocks offer 576 tuning options, which might seem intimidating at first, but after becoming familiar with the settings, they are easy to use and adjust.
I initially set up the system with all four shocks in the middle at 12 clicks. The car rode somewhat firm, but it certainly felt as if I were in control. I wanted a low ride height to accentuate the new Centerline Retro 17-inch billet wheels and Kumho Ecsta Supra rubber that provides the grip. The benefit of coil-overs is that you can run them high, low, or anywhere in between, so they’re the perfect solution for any performance ride.
My setup placed the 24.5-inch-tall tires about 1-inch from the inner fender, and as a result, there would never be enough clearance with a stock system. However, I had enough clearance and therefore no tire rubbing issues with the Global West kit with the exception of at the very end of the testing. During the final stint, I had the steering locked and suspension in full tilt; only a little rubbing occurred.
Sway Bar Upgrade
The 1971 Buick GS was going to be subjected to higher cornering speeds so a sway bar upgrade was in order. I installed an Addco 1⅛-inch front and a 1-inch rear sway bar. Global West also offers factory-size sway bars, making it a simple package purchase. A common mistake when choosing sway bars is to go too large. A sway bar that’s larger than necessary creates more handling problems than it solves. It pulls the inside tire off the ground in a hard corner. Corner entry understeer and corner exit oversteer are just a couple of the problems caused by using sway bars that are too big. Global West does not suggest using a 1¼-inch sway bar with their suspension systems for the GM A-body.
The installation is quite simple and it took less than a weekend to complete. Fitting new components requires more than one set of hands and helpers always make things go a little faster. You need a few tools: a pickle fork to remove the ball joints and an impact gun to remove rusted nuts and bolts.
Handling Improvement
All of the modifications dramatically improve the handling of the car. Not only is cornering improved, but straight-line performance and braking are improved as well. To quantify the improvements, I performed some skid-pad testing using a Vericom VC3000 testing computer.
This computer uses horizontal and lateral accelerometers to measure G-forces and complex formulas to calculate the results. The Vericom is the most accurate data-logging computer of its kind, and the company kindly loaned one to me.
To perform a skid pad test, the car is driven in a large circle, at a steady pace. As each round is completed, the circle is turned tighter and tighter as well as faster and faster. As soon as the rear tires begin to slip, the G-forces are recorded. This is the amount of lateral force that a suspension can handle.
In stock form, the GS recorded .671 G on the skid pad, which is certainly respectable handling. With the G-Plus suspension installed (very little setup was required), the Buick GS convertible pulled 1.04 Gs, which was a vast improvement. At 1 G, you really feel the cornering forces and it was very difficult to make the rear slide under consistent power. Of course, with more than 400 horses on tap, a quick mash of the pedal would certainly get things hairy pretty quickly.
Under hard cornering, the GS now sticks hard to the road and feels like it’s on rails. The steering is tighter with the improved geometry. The bumps that used to send me bouncing out of the seat are now handled with ease, quite surprising considering the extremely low stance I set for the coil-over springs.
Once the car is done, I plan on hitting a couple of open-track days to see how capable the GS really is. Until then, the back roads will just have to do.
Project: Installing an A-Body Axle with Tubular Arms
Stock control arms (top) are made of stamped steel and they flex and deflect, changing the geometry of the suspension when under load. The aftermarket tubular control arms (bottom) are made of high-strength steel alloy; but more important, the tubular design provides much greater strength over the stock control arms. In addition, the tubular arms afford adjustability to the suspension for particular street or competition conditions. The uppers are adjusted to match the factory length.