One of the many attributes that Pontiac owners enjoy is superb driving dynamics. Being dubbed the "Wide Track Division," meant the Pontiac owner was provided a balance of handling, stopping, and ride quality that the competition could not match. The factors that create this equilibrium are the design elements of the suspension and undercarrage of the automobile. Even though, the A-body, F-body, and X-body (among others) chassis configurations were shared with other GM divisions, each tuned their suspension systems via spring rates, shock settings, swaybar sizes, and bushing firmness. This provided each division's models with their own feel and handling characteristics on the road. Anyone who has driven a Pontiac knows that it's much more than a straight-line machine.
Pontiac engineers excelled at providing crisp maneuverability, while dampening road shock without sacrificing a boulevard-style ride. This is not an accomplishment to take lightly. Ride and handling are often diametrically opposed-what improves one area often creates a negative effect in another. There is more to handling than a set of firm springs and bushings when the car will be driven on the varied road surfaces that are encountered during daily use.
With a properly operating suspension system, you can enjoy the driving attributes your Pontiac provided when new. Given modern technology, the result can even surpass the original feel from Pontiac.
Tire technology, which directly impacts the suspension, has advanced greatly over the past decades. A modern radial tire does not need to sacrifice ride quality and impact absorption for handling and braking attributes. But before your Pontiac can provide outstanding rideability, you need to confirm the condition of the entire suspension, not just the obvious parts. With this in mind, HPP traveled to Dimension Frame and Unibody, in Hackettstown, New Jersey.
Proprietor Roy Wilson has made a career out of working with suspension systems and is very familiar with the Pontiac design. Though with photos it is difficult to show the actual wear which will create a sloppy suspension, we used Chris Coffaro's regularly driven '68 GTO as an example to establish the proper procedures to check the suspension. This primer is simply meant to educate our readers on what to look for when examining a Pontiac suspension system, and does not cover any parts replacement or installation steps.
The Thought Process
As is common when you are trying to achieve the best results from any mechanical apparatus, the tolerances that are accepted are tightened up dramatically. When it comes to the suspension, any extra play should be considered unacceptable and will need to be eliminated. Loose suspension joints are the result of wear and will need to be replaced. There are no adjustments that can be made (except to the steering box). Loose pivot joints and bushings will create a sloppy fit that will be greatly magnified by the mass of the Pontiac and the lateral forces that are applied on the road. A joint that may not appear loose when being checked with a pry bar can move when a 4,000-pound Pontiac is whipped into a turn on a highway exit ramp. For this reason, the suspension components should be considered consumables and need to be replaced long before an excessive amount of play is apparent.
On a traditional Pontiac, the front suspension consists of:
• Upper and lower ball joints
• Upper and lower control arms and bushings
• Center link
• Pitman arm
• Idler arm
• Inner and outer tie rods
• Shock absorbers
• Coil springs
• Stabilizer bar and end links
The rear suspension is less complex and is comprised of:
• Shock absorbers
• Coil/leaf springs (depending on application)
• Control arms and bushings (depending on application)
• Stabilizer bar and end links (depending on application)
To gain some insight as to...
To gain some insight as to potential suspension problems, visually inspect the front tires for an uneven wear pattern and run your hand over it to feel for any anomalies. Extreme center wear reveals over inflation, while under inflation will impact the outer area of the tread only. If the tread is worn on one side only or is scalloped, then either the alignment is off, the wheel bearings are worn or not properly adjusted, or there is wear in the suspension.
Check the tread depth with...
Check the tread depth with a gauge available for less than $7 at any auto parts store. Depth shouldn't be less than 2/32-inch (4/32-inch is a bit safer). Measure each groove across the tread to check for uneven wear. Tire age is also a consideration, so check them for dry rot and remember, they can still deteriorate in ways that you can't see. The current popularly accepted tire age limit is 6 years from its production date (posted on the sidewall), even if the tread depth is still within spec.
With the Pontiac parked on...
With the Pontiac parked on a level surface, measure from the ground to each fender lip to check the ride height. If the vehicle is leaning to one side more than 3/4-inch, the springs need to be replaced (in pairs). Make sure any excessive weight is out of the vehicle before measuring.
Visually inspect the upper...
Visually inspect the upper (arrow) and lower control arm bushings for damage and/or dry-rot cracking. On this GTO, visible results of dry rot mean that they need to be replaced. Even if the bushings look good, use a prybar to exert some pressure on the control arm to see how much the bushings deflect, Since they are rubber, some movement is to be expected, but if it's more than an 1/8-inch, they should be replaced.
With the car jacked up and...
With the car jacked up and supported under the lower control arm, and the front tire off the ground, check the wheel bearings for looseness by grabbing the tire at the top and bottom and alternately pushing in and pulling out in both areas. If the wheel and tire rock back and forth noticeably (there will be some inherent play since the tapered wheel bearings are not preloaded), mount a dial indicator on the nut and the plunger on the wheelhub; repeat the test. If the measurement is greater than 0.005-inch, the wheel bearings are loose and need to be adjusted. Also, spin the tire and look for roughness as it turns and listen for clicking or a whirring sound that indicates the bearings need to be removed, repacked with grease, reinstalled, and adjusted, or replaced due to wear.
The upper ball joint resides...
The upper ball joint resides in the upper control arm and was riveted into place by the factory on many models-replacements are bolted in. (This one is grease and dirt covered so you can't see the attaching hardware). Inspect the control arm for cracks or excessive rust.