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Shock and strut diagnosis
The shock absorber/strut is the most commonly replaced component in the suspension system.
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Worn shock safety concerns
Besides ride quality a worn out or failed shock/strut can cause:
Reduced steerability – especially on rough roads
Increased braking distance
Shock/strut noise
Worn shock bushings and attachment hardware will produce a rattling noise when the vehicle is driven over uneven surfaces.
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Visual inspection of shock/strut
Fluid leaking from the area around the seal indicates the seal has failed and immediate replacement is necessary.
A very small amount of fluid ‘mist’ around the seal is normal, but liquid coating the upper part of the shock is definite sign of seal failure.
Check for worn or broken rubber bushings.
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Worn or damaged jounce stops
Split, cracked or damaged jounce stops are a sign of worn shocks and or springs.
Jounce stop
Damaged dust bellows
Since the jounce stop is often integrated with the dust bellows a damaged, broken or torn dust bellows is a sign that the strut has lost dampening ability.
Polyurethane jounce stop
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Shock diagnosis
After a visual inspection of the shocks and suspension a road test is needed to assess the dampening ability of the shock.
Symptoms of worn shocks:
Excess pitch and roll oscillations after encountering bumps in the road.
Excessive dive during braking or squat during acceleration.
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Rattling noise on uneven surfaces
Clunk noise when the vehicle is steered left and right
Notchy steering or frozen steering
Pull to either side
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Checking strut mounts
With the vehicle raised so that the tire is about 1 inch off the floor pry the tire upward to take some of the load off the mount.
Pry the center of the mount side to side to measure lateral freeplay.
Pry the whole strut up and down to measure axial freeplay
Axial freeplay
Lateral freeplay
Ball joint lubrication
Most modern passenger cars are built with sealed ball joints and tie rod ends that are greased for life and require no maintenance.
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Chassis lubrication
Heavy trucks normally have grease-able joints on all the suspension and driveline components.
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NLGI grade number
Chassis grease standards are set by the National Lubricating Grease Institute
There a 9 grades ranging from 000 to 6
The higher the number the thicker the grease.
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NLGI grade number
Grease that is too thin will leak out of the joint.
Too thick and the grease cannot work its way in-between the ball and seat.
GL-1 and GL2 are the types of grease normally used in suspension and steering joints.
GL-2 has the consistency of peanut butter.
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Zerk fitting
The only way to grease a ball joint is through a Zerk fitting.
The Zerk fitting couples the grease gun to the joint.
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Grease guns
Shops that work mostly on passenger cars will normally use hand operated grease guns as there are very few applications on modern cars that require periodic greasing.
Shops that work mostly on trucks will have pneumatically operated grease guns that save time when a vehicle has several dozen grease fittings.
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Ball joint boots
Most modern passenger cars have sealed boots that a clamped tight to the ball joint with spring steel clips.
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Ball joint boots
Older cars and trucks may have loose fitting ‘umbrella’ type boots that allow a small amount of grease to leak out of the skirt.
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Ball Joints – visual inspection
A ball joint should last indefinitely if the rubber boot that retains the grease and keeps dirt and moisture out remains intact.
Any visible damage to the rubber boot is reason enough to replace the ball joint.
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Checking ball joints for wear
If the spring is positioned on the lower control arm the upper and lower ball joints are under tension when the wheels are off the ground.
Place a jack stand under the lower control arm as far outboard as possible.
After lowering the vehicle on to the jack stand if there is a gap between the rebound stop and the upper control arm the ball joints are now unloaded.
Gap between the rebound stop and upper control arm
Frame
Checking ball joints for wear
If the spring is positioned on the upper arm the ball joints will be unloaded then the wheels are off the ground.
The rebound stop will be in firm contact with the upper arm.
Frame
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Freeplay measurements are made between the steering knuckle and ball joint/control arm in both axial and lateral directions.
Dial indicator setup to measure lateral freeplay
Lateral freeplay
Specifications for ball joint freeplay can be found in AllData.
Measuring ball joint freeplay
Axial freeplay
Threaded
Rivets
Bolts
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Press fit and threaded ball joint
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Ball joint retained by rivets
Alternatively the heads of the rivets can be ground off using a die grinder.
Never cut the rivet heads off with an oxy-acetylene torch.
The new ball joint is retained with bolts and nylock nuts.
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Integral and bolted ball joints
Ball joints that are retained by bolts are commonly found on vehicles with MacPherson struts.
Integral ball joints are bolded directly o the control arm.
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The ball stud is slightly tapered.
After the retaining nut has been removed several tons of force will be needed to separate the ball stud from the steering knuckle.
Ball stud
Hammer method
This technique can only be used on forged steel steering knuckles.
Strike the steering knuckle on the area surrounding the ball joint tapered stud with the flat side of a 5 lbs, ball peen hammer.
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Pickle fork method
This technique will destroy the ball joint’s rubber boot so it is only used when replacing ball joints.
A similar forked tool can be used with a pneumatic hammer.
Like the hammer method this technique should only be used on forged steel steering knuckles.
Ball joint separator – AKA Pickle Fork
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Screw type ball joint separator
A steel disc positioned between the ball stud and the pushing screw distributes the force on the stud evenly.
The screw type separator does not damage the rubber boot or ball stud threads.
Many technicians back of the retaining nut 3 or 4 turns but leave it on the ball stud to protect the threads of the stud.
Steel disc protects the threads of the ball stud
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Screw type ball joint separator
The are a number of screw type ball joint separators available to fit most applications.
Images courtesy of OTC Corp.
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Pinch bolt retained ball joints
Pinch bolts are often used to retain the ball joint stud to the steering knuckle.
A slot is cut through the steering knuckle into the ball stud hole.
A pinch bolt squeezes the steering knuckle tight to the ball stud,
The pinch bolt passes through a groove in the ball stud – insuring that the ball joint stays attached to the knuckle even if the bolt loosens.
Groove for pinch bolt
Ball joint press
A ‘C’-clamp type press is used to press the old ball joint out and press the new joint in while the control arm is still attached to the frame.
Images courtesy of OTC Corp.
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Pressing out ball joints
Press fit ball joints can be serviced on-the-car with a C-clamp type press or off-the-car using a hydraulic shop press.
A receiver sleeve is needed to support the control arm.
The receiver must be large enough to accept the large end of the ball joint.
1.875”
2.000”
Ball joint press
The receiver sleeve is often notched to allow clearance where sections of the control arm are very close to the ball joint bore.
A ram sleeve is needed to apply even pressure to the smaller end of the ball joint.
Ram sleeve
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Ball joint press - removal
The inner diameter of the receiver must be slightly larger than the outer diameter of the ball joint.
The ram needs to be slightly smaller than the ball joint bore in the control arm.
Receiver
Collar
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Ball joint press - installation
For installation we need to select a ram sleeve that fits the outer body of the ball joint.
The ram sleeve must contact on this part of the ball joint
Appling pressure to the softer metal parts closer to the center will damage the new ball joint
Images courtesy of OTC Corp.
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Ball joint press - installation
The receiver sleeve must be long enough to accept the full length of the ball stud.
The inside diameter of the receiver must slightly larger than the small end [un-flanged]of the ball joint.
Receiver sleeve
Castellated nut and cotter pin
The correct way to install the cotter pin on a castellated nut is shown on the left.
The excess on the lower side of the cotter pin is cut off with diagonal pliers before bending.
Correct
Incorrect
Ball joint R&R
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Use a jack stand for safe removal
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Pressing out the ball joint
Do not use an impact wrench with any type of screw press. Using an impact wrench damages the threads
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Control arm after removal
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Installing the new ball joint
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Install the pressing adapter
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Pressing in the new ball joint
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Check for gaps
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Boot orientation
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Install the boot
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Install Zerk fitting
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Riveted type ball joint
The upper ball joint on this vehicle uses a riveted type joint.