Tech Tips
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Saab
SAAB SUSPENSION SERVICE:
ENSURING THE INTEGRITY AND RESPONSIVENESS OF CHASSIS COMPONENTS
Edited from an article by Boe Kalinoski, Import Specialist, ImportCar Magazine, April 2002
Saab has always considered the responsiveness of the chassis the first part of safety. The strong, stiff structure was first designed on the Saab 99 in 1969 and it was carried over to the 900 series. Those vehicles share the same ball joint and control arm design.
The structure had relatively direct steering for good road feel. The front wheels have an independent suspension; the hub and driveshafts are mounted on a double-row, angular-contact ball bearing in the steering knuckle.
The steering gear is a power rack unit designed by GM for Saab in 1979. In the past, when the unit was cold it had some problems with fluid leaks and hard steering, but it was redesigned in 1987 with improved spool valve seals and a housing that was made from cast iron.
The steering knuckle housing is reconnected to the control arms by means of permanently lubricated ball joints. The inner ends of the control arms are seated in rubber bearings at the body. The outer CV joint is splined and force-fitted to the hub and is protected with a rubber boot.
In 1985, a front sway bar was added. It proved to help in road holding and stability as engine power increased over the years. The outer end of the sway bar is connected to the lower ball joint mount bolts using an odd-style bracket/bushing configuration.
The shock absorbers prove to do their job well in this front-end arrangement. Saab uses gas/fluid-filled units that outlive ball joints and other major front-end components. The only service they need is replacement of the lower mount bushings, as they tend to wear out and cause a clunking noise like a worn-out ball joint.
Anti-lock braking systems were featured on all models beginning in 1990. The wheel sensors on these vehicles are mounted in the steering knuckle and the wheel sensor is part of the outer CV joint. The rear axle hub carries the rear sensor wheels.
When removing the knuckle or replacing the wheel bearing, the sensor also must be removed. Over a period of time, they tend to seize in their mounting hole and may have to be replaced.
The rear suspension uses a straight axle with lower control arms, coil springs, trailing arms and a Panhard bar. The rear axle has no adjustments; it is a fixed design. The centerline of the spindles and axle tube are offset and tend to bend when the vehicle travels over rough roads and while carrying heavy loads.
I have designed a special jig using a small hydraulic 10-ton jack (see Fig. 1). While the car is on the four-wheel alignment machine, I hook this up to the rear axle and see the live readings changing on the screen. This tool allows me to bend the axle tube to compensate for the spindle/axle area that is out of range. The only other method is to replace the axle, which can be costly.
Before any service work is done to the suspension, the car should be road tested to reveal problems that may not be noticed during service procedures.
To detect ball joint play on the front end of the 900, the control arms must be relieved of the tension imposed by the coil spring. Fit tool insert 8393209 under the top control arm. Check axial play in the top and bottom ball joints by using a pair of large water pump pliers to compress the ball joint. Maximum axial play is 2 mm.
Check radial play in the top and bottom ball joints by inserting a lever between the control arm and the steering knuckle. Take care not to pinch or damage the rubber seal. Maximum radial play is 1 mm.
Note: If any service work will be performed on the front suspension, the insert tool must be used! If it is not used, the coil spring could come out of its seat and cause severe bodily injury.
When replacing the ball joints, install new bolts and lock nuts. Most aftermarket ball joints are sold as a kit with the hardware included.
Check all shock bushings and sway bar end bushings for wear. We replace them with a urethane-type plastic, as they last twice as long as rubber and give better road feel.
If the control arms have been subjected to violent stresses as the result of a collision or the like, they must be inspected carefully for signs of failure or distortion. Also, control arms on high-mileage cars tend to crack from metal fatigue.
Some minor problems can occur with the wheel alignment such as when the bolts that hold the upper control arms and shims in place become frozen or rusted. These bolts are in obscure areas, making the job a little tough.
THE NEW-STYLE 900
The new body style of the 900 series was introduced in 1994. It has a completely different chassis/suspension design (see Fig. 2). It is a MacPherson-type with aluminum lower control arms with built-in ball joints.
In 1995, Saab introduced front suspension part kits to retrofit the 1994 and later 900 series to eliminate noise and vibration from the front assembly (Tech Bulletin 731-1821). The bulletin and kits solve common customer noise complaints like ticking, scraping, thumping and creaking coming from the front end. The lower control arms, strut rods and sway bar were also redesigned for the 1995 model year. It is a trouble-free system and only toe can be adjusted.
Common problems with the 900 series involve the lower control arms/ball joints and upper strut mount failure. It’s a good idea to keep some outer tie rod ends on hand as they have a tendency to seize on the steering rack and make adjustments difficult.
SAAB 9000 SUSPENSION
The Saab 9000 has a unique front suspension. It swings down on the left side for ease of transmission removal. It has stamped-steel lower control arms and bolt-in ball joints (see Fig. 3). The rear of the control arm has a bushing pressed into an aluminum housing, which exhibits often-overlooked problems, resulting in excessive tire wear and poor handling.
The front struts can last for well over 100,000 miles but the upper bearing mounts seem to clunk and loosen up, so they should be checked before any alignment work is done.
Checking chassis height is always important. Our alignment machine has a built-in check for this purpose. Chassis height affects other alignment angles, so its accuracy is just as important as accuracy in setting the alignment angles. It is the foundation for static camber, caster and toe settings, and also controls dynamic changes in the angles of primary camber and toe. If it is not properly maintained, tire wear and handling can be affected.
Our alignment machine also reveals the condition of the springs. Weak springs always should be installed in pairs as it would be impossible to regulate equal height without the use of spacers, which I don’t recommend.
After any front-end work is done, the technician should perform a four-wheel alignment, starting with checking tire air pressure and the condition of the tires.
Next, check the rear wheel alignment, rear camber, rear toe, caster/camber on the left side, caster/camber on the right side and, finally, the front toe.
It is a good practice to road test the vehicle after the alignment, making sure that the steering wheel is straight and no pulling is noted. In that way, you will ensure a quality repair and customer satisfaction with the job.
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