• 2016

THEIR RIDE QUALITY DEPENDS ON IT

Quite often, suspension problems sneak up on a vehicle owner. Struts, shock absorbers and bushings wear out gradually. It’s not until new struts are installed that the owner realizes the struts were, in fact, worn because now their car rides so much better. Truth be told, worn pieces can be detected before the ride quality of the vehicle noticeably deteriorates.


SUSPENSION BASICS

Figure1The objective of all basic front and rear suspension designs is the same — to provide a smooth, comfortable and safe ride. Minivans, like many FCA US LLC vehicles, use a McPherson-style strut and single lower control arm design in the front. These vehicles use a solid beam rear suspension, while cars, such as the Dodge Dart, have an independent rear suspension utilizing a lower control arm and shock absorber. The Chrysler 300 and its companion vehicles (the Dodge Challenger and Charger) uses unequal length control arms in the front (Figure 1), but a 5-link independent design in the rear.

There isn’t one basic front suspension design, or one basic rear suspension design used across the product line, but all of these designs use the same components. These include control arms, ball joints, struts and shock absorbers, stabilizer bars, coil springs and bushings. Rarely do any of these components fail suddenly, unless the vehicle is driven in extreme conditions (e.g. off road), or encounters a well hidden city pothole. Rather, suspension components wear out over time. Over the life of a vehicle, two components that might require replacement are bushings and ball joints.

BUSHINGS

Bushings are located at any mounting point for a front and rear suspension component. Mounting points Figure2that require bushings include control arms, stabilizer bars and trailing links. The front control arm will have two pivot points that use bushings. On a Dodge Challenger or Charger, that’s four control arm bushings (upper and lower control arms) on each side of the vehicle.

Bushings should be checked whenever the vehicle is on a lift for service. Bushings are found in most locations where an arm or bar is connected to the frame. Sway bar, or stabilizer bar, bushings are notorious for wearing out, often needing replacement at 50,000 miles (Figure 2). Often, the clunk heard on an older vehicle when it moves over a bump in the road is a sway bar moving within a worn out bushing. Bad bushings are distorted, cracked and/or have splits in the material. Check all the bushings, front and rear.

BALL JOINTS

Figure3The ball joint is a movable connection, like a ball and socket, between the control arm and steering knuckle. Due to the movement within the joint, it very slowly wears over time. Wear can be accelerated, though, if the protective boot, shown in (Figure 3), is damaged. This allows the grease to become contaminated, accelerating wear. Checking ball joints varies from vehicle-to-vehicle, so check the appropriate service manual. Let’s review the procedure for checking the ball joints on the Chrysler 300, Dodge Challenger or Charger rear wheel drive (RWD) vehicles, as these cars have 6 ball joints (2 lower and 1 upper on each side).

One lower ball joint is for the lower control arm and the other lower ball joint is for the tension strut. The ball joint for the lower control arm is pressed into the knuckle and the ball joint for the tension strut is part of the tension strut. The ball joint for the lower control arm can be replaced as a separate component of the knuckle. The tension strut ball joint can only be replaced with the tension strut. Inspect the lower ball joints for wear in the following manner:

Note: These test procedures are for RWD cars only

1.Remove tire and wheel assembly

2.Attach a dial indicator to base of tension strut, then align the dial indicator’s contact pointer with direction of stud axis and touch machined flat on knuckle near ball joint; zero the dial indicator

3.Attach a second dial indicator to base of lower control arm, then align the dial indicator’s contact pointer with direction of stud axis and touch machined flat on knuckle near ball joint; zero the dial indicator

4.Insert a pry bar and rest it against lower control arm or tension strut (depending on which is being tested); use lever principle to push knuckle upward until dial indicator no longer moves

Note: Use care when applying the load to the knuckle so as to not damage components of suspension

5.Record any ball joint movement; if movement in the lower control arm exceeds 0.059 in., the ball joint is worn and must be replaced

The upper ball joint is pressed into the upper control arm. It is sealed for life, in the same manner as the lower ball joints, and cannot be lubricated. Neither the upper ball joint, nor the seal boot can be serviced as a separate component. The entire upper control arm must be replaced if either are damaged, or worn. Inspect the upper ball joints for wear in the following manner:

1.Remove tire and wheel assembly

2.Attach a dial indicator to body of upper control arm, then align dial indicator’s contact pointer with direction of stud axis and touch machined flat on end of knuckle near ball joint; zero the dial indicator

3.Insert a pry bar and rest it against bottom of upper control arm and use lever principle to push arm upward until dial indicator no longer moves

Note: Use care when applying the load to the knuckle so as to not damage components of suspension

4.Record any ball joint movement; if movement in the control arm exceeds 0.059 in., the ball joint is worn

5.If the ball joint needs replaced, the entire upper control arm must to be replaced

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