When customers evaluate shop performance, they tend to lean most heavily on two sensory responses, look and feel. Shops focus heavily on the first as they return cracked, bent and broken finishes and parts to factory specs using the latest technology and training. This focus makes sense. The first thing customers are going to notice in a repair is the vehicle appearance.
Feel can be just as significant. In fact, in the days and week that follow a repair it can surpass look. The feel here is the responsiveness of the vehicle, how well it handles and responds to driving conditions compared to its pre-accident state. If it feels the same (or better), customers are satisfied. If unfamiliar responses or nagging difference between its pre- and post-repair condition crop up, customers are either going to complain directly to your business or share negative criticism with friends and family who likely could take your services off their preferred automotive providers list.
There’s an easy solution to avoiding the latter issue: Follow the factory specs. Suspensions, particularly front suspensions, are interesting creatures. They’re both rugged and sophisticated, tough and sensitive. They do a great job in handling rough road surfaces. When a jolt comes from elsewhere, particularly the kind produced to the front or side of the suspension during a collision, they are susceptible to serious damage—or at the least, damage that must be addressed during a collision repair.
You’ll want to pay stricter attention to front suspension during pre-repair damage analysis and post work evaluations and road tests. You also may need to reevaluate how closely your shop sticks to OEM repair guidelines for each of the vehicle models you repair.
Here’s a look at control arm and stabilizer bar replacement in a popular compact vehicle, the new Chevy Cruze, using instructions provided by GM. Use the lessons learned here, particularly the need to use specialized tools and precise calibrations, in all your suspension work.
Note: Refer to GM recommendations for regional tools in the event you need replacements for the ones mentioned here.
Background: Keeping you in suspense
Why are front suspensions designed as they are and how does that affect how they are repaired? Funny you should ask. Understanding the answers to these questions is one of the keys to successfully performing suspension work.
Vehicle front suspensions essentially have two jobs: (1) isolate vehicle occupants from harsh road surfaces while (2) keeping wheels horizontal to the road to provide effective handling. Suspensions handle the first task in large part by absorbing and dissipating energy through springs, shocks and struts. The second job is performed using a series of bearings, joints and metal structures that allow the suspension to pivot and react to changing driving conditions.
Significant here is the work of the control arms (upper and lower, left and right), which join the rest of the suspension to the vehicle frame. The control arms create an A-shaped design, with the inner part of the lower arms running from the frame where they attach, often, at two points through semi-rigid bushing. The outer part of the lower control arms link to the steering knuckle whose upper portion attaches to the strut assembly—which then connects to the vehicle body via a bearing. The steering knuckle moves up and down independent of the frame.
Connecting the left and right lower control arm assemblies is the stabilizer bar (shaft). This bar dictates the amount of independent movement of the suspension when the vehicle turns (the amount of vehicle roll), which in turn defines how a vehicle handles when making turns.
This setup permits a vehicle to both roll on its tires and alter direction while supporting the vehicle and providing a smooth, controlled and comfortable ride. This structure is standard across the automotive industry. Ride characteristics, however, can vary widely between different types and models of vehicles based upon how a particular suspension is tuned—how the parts comprising it are designed and engineered to work together to create a particular driving experience.
The goal in repairing a front suspension is restoring this experience, recreating exactly the interaction of all these moving pieces to one another and the vehicle itself. The object here is following the OEM instructions and recommendations exactly as they are documented as you remove damaged suspension parts and replace them with new ones.
Replacing lower control arms
Removal
- Raise and support the vehicle. Refer to GM instructions for Lifting and Jacking a Vehicle.
- Remove the tire and wheel. Refer to GM instructions for Tire and Wheel Removal and Installation. Note: Do NOT re-use the lower control arm bolts and nuts. Discard and use NEW only.
- Remove the wheel speed sensor wiring harness from control arm and steering knuckle.
- Remove and discard the lower ball joint to knuckle nut and bolt.
- Separate the lower control arm from the knuckle.
- Remove and discard the front lower control arm nut and bolt.
- Remove and discard the rear lower control arm bushing nuts and bolts.
- Remove the lower control arm from the front frame
Installation
- Position the lower control arm in the cradle.
- Install and hand tighten the new rear lower control arm bushing nuts and bolts.
- Install and hand tighten the new front lower control arm nut and bolt. Caution: Refer to Fastener Caution in the Preface section.
- Support the lower control arm with a hydraulic jack and lift the control arm into the neutral position.
- Tighten the front lower control arm bolt to 70 N·m (52 lb ft) +75-90 degrees , using a 45059 torque angle meter.
- Tighten the rear bushing to frame bolts to 55 N·m (41 lb ft) +45-60 degrees , using the torque angle meter.
- Install the NEW ball joint to knuckle bolt and nut and tighten to 30 N·m (22 lb ft) +60-75 degrees, using the torque angle meter.
- Lower the vehicle to the ground in order to tighten the control arm fasteners correctly.
- Remove the jack stand.
- Install the tire and wheel, referring to GM instructions for Tire and Wheel Removal and Installation.
- Lower the vehicle.
Replacing the stabilizer bar
Removal
- Turn the front wheels to the straight forward position and secure the steering wheel from moving.
- Remove the lower steering intermediate shaft bolts.
- Remove the steering intermediate shaft from the steering gear.
- Raise and support the vehicle, referring to GM instructions on Lifting and Jacking the Vehicle.
- Remove the tire and wheel assemblies, referring to GM instructions on Tire and Wheel Removal and Installation.
- Remove the front compartment insulator, if equipped, referring to GM instructions on Front Compartment Insulator Replacement.
- Remove the exhaust flexible pipe, referring to GM instructions on Exhaust Flexible Pipe Replacement.
- Remove lower stabilizer link shaft nut on both sides.
- Remove stabilizer link shaft from the stabilizer shaft.
- Remove the stabilizer link shaft from stabilizer.
- Remove the four fasteners for the engine side cover on both sides.
- Remove the four fasteners for the front engine compartment cover.
- Remove the front and the rear transmission mount bracket bolts.
- Remove and discard the two rear suspension frame bolts.
- Remove the rear frame reinforcements.
- Position and set the hydraulic lifter in connection with CH-904 frame tool and CH-49289-50 adapter tool onto the suspension frame. Pull away the front engine compartment cover slightly.
- Lower the suspension frame a maximum of 55 mm.
- Remove the four front stabilizer shaft insulator clam bolts.
- Remove the stabilizer shaft.
Installation
- Install the stabilizer shaft.
- Install the four front stabilizer shaft insulator clam bolts (1) and tighten to 22 N·m (17 lb ft) plus 30 degrees.
- Move out the positioning pins of the CH 49289 adapter tool.
- Raise the frame carefully, using the CH 49289 adapter tool.
- Install the two frame reinforcements.
- Install the two new frame rear bolts (2) and tighten to 160 N·m (119 lb ft). Note: Do NOT reuse old bolts.
- Install the front transmission mount bolt and tighten to 58 N·m (43 lb ft).
- Install the rear transmission mount bracket bolt and tighten to 100 N·m (74 lb ft).
- Install and tighten the four fasteners of the engine side cover on both sides.
- Install and tighten the four fasteners of the front engine compartment cover.
- Install the front compartment insulator, if equipped, using GM instructions for Front Compartment Insulator Replacement.
- Install the exhaust flexible pipe, referring to GM instructions on Exhaust Flexible Pipe Replacement.
- Install and tighten lower stabilizer link shaft nut on both sides to 35 N·m (26 lb ft).
- Lower the vehicle.
- Install the tire and wheel assemblies, referring to GM instructions on Tire and Wheel Removal and Installation.
Finishing moves
Polish off any suspension work with a thorough test drive. Take the vehicle over a variety of road surfaces at different speeds, monitoring the handling and response, while taking note of any remaining problems.
Also, always speak to customers directly about suspension work. In some cases and for certain repairs, you’ll need to remind them that the suspension will feel a bit different because of the new parts but will gradually settle into a more familiar feel as the parts adjust. This talk can take just several minutes while saving your customers and shop some significant headaches and anxiety.
It’s the same case with taking the extra time to perform these repairs as the manufacturer intended. Take this course, and no one will be kept in suspense of any potential negative fallout from this detail-intensive work.
