Archives March 2025

Ball joints have been on most vehicles for more than 70 years. They were replacements for kingpins, but they also became essential for independent suspensions.

While the basics of the ball joints have remained the same, the materials have improved along with design refinements that enable the joint to last longer and carry greater loads. In the aftermarket, some manufacturers have focused on improving the OE designs and adding serviceability to the joint.

Materials Matter

All ball joints manufactured in the past 70 years have benefitted from better materials that improve every year. High-tech elastomeric materials are now used on most ball joint boots instead of basic rubber. These materials remain more pliable under different temperatures and help to keep a wide range of motion longer.

These materials can withstand heat from the brakes and environmental dangers like ozone and fluids better than their predecessors. With better engineering tools, the designs of the boots have resulted in more compact packaging.

Another element that has improved is the methods of sealing the boot to the base and stud. In the past, many boot designs were a friction fit, where the elasticity and bellows of the boot held it in place. Over time, the materials would lose their elasticity and no longer have the ability to seal the boot against the elements.

New boot designs are using metal rings to hold the boot in place. Some aftermarket manufacturers are engineering the boot and joint together with slots in the base and stud to secure the boot.

The Boot

The materials used to manufacture ball joint boots have improved by leaps and bounds. New materials can last longer in extreme conditions while having the same range of movement. New material and boot designs seal better and can retain grease longer.

On both sealed and greaseable joints, the boot is the most vulnerable part. If a boot is torn or is no longer adequately retained on the stud or body, moisture and contamination can enter the joint.

Inspection of the boot is just as important as measuring play. Looking for damage might require running your finger around the boot. The advantage of the greaseable joint is that when the joint is filled with grease, the grease will escape out the hole.

How the boot is retained on the stud and base has also improved. Some ball joint manufacturers have reduced the size of their boots to minimize the possibility of boot damage and to enhance retention of the boot on the stud and base.

When installing a ball joint or boot, look at the manufacturer’s instructions and recommendations. Some boots are retained by a lip on the ball joint’s body, while others may use a snap ring at the top or bottom. Using universal boots is never recommended. These may not offer the same range of motion and expose the joint under certain conditions.

Grease

All ball joints have one thing in common: grease. Grease reduces friction and wear on the surfaces of the ball and socket. For greaseable joints, it is recommended that a National Lubricating Grease Institute (NLGI) certified GC/LB rating is used for ball joints. This grease is designed to withstand extreme pressures, oxidation and prevent corrosion. Use of a general purpose or non-certified chassis grease will not offer the same level of protection as a NLGC GC/LB certified grease.

Flushing the Joint

When you are lubricating a ball joint through the Zerk fitting, you are not just “topping off” the grease. The grease can flush debris and moisture out of the joint. This is one of the main advantages of a greaseable joint.

Most greaseable joints have a relief valve where the boot meets the stud. When grease is pumped into the joint, the old grease will be forced out the relief valve. The right amount of grease in the joint and boot acts as a seal that occupies space that water and debris could take up. Pump only enough grease until fresh grease can be seen coming out the relief valve.

If the grease is not coming out of the top of the boot, do not keep pumping. The pressure inside the joint can dislodge the boot from the base. Try clearing the relief valve with a blunt pick to remove the obstruction.

Inspection

To check a loaded ball joint, place a jack or jack stand under the lower control arm to support the weight of the vehicle. Attach a dial indicator to the lower control arm and set the dial in a vertical position to measure axial runout at the steering knuckle. In the case of an all-wheel-drive front ride strut or independent RWD, it may be necessary to mount the dial at the CV joint. Moving the steering knuckle can check lateral runout.

For a short/long arm (SLA) suspension that has the coil spring over the top arm, the upper joint is loaded. To check the joint, the upper control arm is supported to unload the joint. If the ball joint has a built-in wear indicator, joint play should be checked with the vehicle on its wheels. These designs are rare these days.

To check a follower-type joint, the Belleville washer or spring is loaded or compressed to check for axial end play. For a strut-type suspension, place a jack stand under the cradle to allow the strut to fully extend. Attach the dial indicator clamp to the lower control arm and set the dial in a vertical position to measure axial runout at the steering knuckle. Place a jack under the ball joint and load the joint by raising the jack. Turn the steering wheel and observe the ball joint to check lateral runout.

For an SLA suspension, the upper control arm can be blocked, and the joint can be compressed. Attach a dial indicator to the steering knuckle and place it in a vertical or parallel position to measure axial runout at the lower control arm. Moving the steering knuckle can check lateral runout.

Installation

In theory, an impact should never be used to install the nut that secures the ball joint’s stud to the knuckle. This can damage the joint by heating it up due to friction. The heat and motion can hurt a plastic joint inside the joint and even the sintered metal bearings. Even if the joint is metal on metal, the fast rotation can displace the grease.

 It is for this reason that OEMs and aftermarket chassis suppliers have tiny bolt heads or recessed Allen heads to hold the stud while the nut is tightened. Some aftermarket manufacturers are including wrench flats lower on the stud to make installation easier.

Stud designs have changed to accommodate aluminum knuckles. If you see a ball joint stud with a 45-degree taper and a long-threaded stud, chances are it is going into an aluminum knuckle. These typically have torque angle specification that recommends an initial torque specification followed by an angle. Failure to use the correct procedure will result in a broken fastener or a loose joint that can damage the knuckle.

The technician shortage is no secret, but the solution might be closer than you think. In a recent Tomorrow’s Technician Partnership Pathways podcast, Van Harris, a regional sales rep for NAPA Auto Parts, shared how strong partnerships between schools, shops, and suppliers can help secure the future of the industry.

Harris has been working with automotive training programs for over two decades, helping schools like Chapel Hill High School transform their programs from underfunded afterthoughts into thriving pipelines for skilled technicians. Under the leadership of instructor Robert Ballard, the program has grown from 50 students to over 300, thanks in part to strategic industry support.

Why Should Shop Owners Care?

Harris makes a powerful case: if today’s repair shops don’t invest in technician training, they won’t have a workforce tomorrow. He regularly brings shop owners, dealership representatives, and industry leaders into classrooms to showcase the talent being developed and encourage them to engage with students directly.

Shops that get involved now can:
✅ Build relationships with future techs before they enter the job market.
✅ Help shape training programs to ensure students develop real-world skills.
✅ Create mentorship and apprenticeship opportunities that benefit both students and businesses.

How Can Shop Owners Get Involved?

1️⃣ Join advisory boards – Schools need input from industry professionals to shape their programs.
2️⃣ Offer hands-on training – Loaning tools, donating equipment, or providing shop tours can make a big impact.
3️⃣ Mentor students – Encouraging young talent and offering internships builds a stronger workforce.
4️⃣ Support diversity in the trade – With 33% of students in Ballard’s program being female, now is the time to foster inclusive opportunities.

Harris emphasizes that this isn’t charity—it’s an investment. As he puts it, “If you don’t invest in this, you won’t have a business in 10 to 15 years.”

The Bottom Line

Shops that take an active role in training the next generation will be the ones with the skilled techs needed to stay competitive. If you’re not already working with a local school, now’s the time to start.

#AutomotiveIndustry #FutureTechnicians #InvestInTalent #ShopOwnerSuccess #WorkforceDevelopment

Vacuum brake boosters will probably be with us for a long time. It is the most efficient and economical way to amplify the force exerted by the driver. But where the booster gets its vacuum is changing. Many import and domestic nameplates have been using vacuum pumps to power the brake booster on their gas-, diesel- and even electric-powered vehicles. 

For a vacuum brake booster to work, it needs a source of vacuum. In the past all that was needed was a port on the intake manifold. Now, vacuum pumps are the choice for negative pressure power.

Why a Vacuum Pump?

In every piston engine, vacuum is generated during the intake stroke as the piston goes down in the cylinder and the intake valves are open. But modern engines have changed. Increased efficiency has reduced the amount of vacuum available to the brake booster. Engines have been downsized to 2.0- and even 1.4-liters. This means that there is less displacement to generate the vacuum. 

Variable valve timing has further diminished the vacuum generated because the timing of the opening might be timed to allow a scavenging effect so some of the intake air makes it past the exhaust valve. This air is intended for the catalyst so unburned hydrocarbons can be burned.

Turbocharging has also eliminated traditional vacuum in the intake manifold. The turbocharger produces positive pressure or boost in the intake manifold. The only time an engine might be under vacuum is when the engine is decelerating, and the throttle is closed. 

What Type of Pump? 

Vacuum pumps have been used on diesel engines for more than 40 years, typically as a diaphragm pump. These pumps were neither efficient nor reliable.

Most modern VWs use either an electric vacuum pump or a pump driven by a sprocket connected to the timing chain. These pumps use vanes attached to an offset shaft. As the shaft rotates, the vanes create a sealed chamber with the walls of the housing. 

Since the shaft is offset, the chambers change in volume and produce a vacuum on the outlet side when turned. Electric pumps typically have multiple vanes; timing chain-powered pumps use just one vane. 

Electric-powered vacuum pumps are controlled by the engine control module. The system uses a pressure sensor mounted between the pump and the booster. The ECM will look at the vacuum, brake pedal position and other engine parameters. The vacuum pump is controlled with a relay that is actuated by the engine control module. The pump is turned on for 2- to 3-seconds during startup.

Timing chain-powered pumps are lubricated with engine oil. The oil inlet is next to the shaft and is fed from the oil slung off the timing chain and sucked into the pump through a valve that controls the level of oil. 

While it is rare for the vanes to wear out, it is possible for carbon and debris to enter the pump and cause damage to the vanes and housing. If the vanes can’t seal against the housing, a vacuum can’t be generated. The most common symptom of a worn pump is a hard brake pedal. 

The Booster

No matter if the booster gets vacuum from the engine or a pump, if it is damaged, the brake pedal performance will change. The condition of the diaphragm inside the booster is also important. If it’s cracked, ruptured or leaking, it won’t hold vacuum and can’t provide much power assist. Leaks in the master cylinder can allow brake fluid to be siphoned into the booster, accelerating the demise of the diaphragm. 

If there’s brake fluid inside the vacuum hose, it’s a good indication that the master cylinder is leaking and needs to be rebuilt or replaced. Wetness around the back of the master cylinder would be another clue for this kind of problem.

To check the vacuum booster, pump the brake pedal with the engine off until you’ve bled off all the vacuum from the unit. Then, hold the pedal down and start the engine. You should feel the pedal depress slightly as engine vacuum enters the booster and pulls on the diaphragm. No change? Then check the vacuum hose connection and engine vacuum. If it’s OK, the problem is in the booster, which needs to be replaced.

Electric power steering (EPS) or electric power assisted steering (EPAS) systems continue to rise in popularity among auto makers. Diagnosing these systems can be a challenge. There are a few different types of EPS systems. Some mount the motors onto the steering column, on the pinion shaft against the steering rack, or on a secondary pinion gear on the other side of the steering rack. Despite their differences, they all operate with the same goal: assisting the driver whenever turning the steering wheel.

Let’s take a closer look at the sensors which make up these systems, and how they operate.

The Big Picture

EPS systems apply steering assist force based only on driver input. The system uses input data from a multitude of vehicle sensors to determine how much steering assist force is required. More often than not, the problem ends up being a faulty sensor, wire, or connection somewhere in the system.

The EPS system is connected to the powertrain CAN-BUS, and communicates with a number of systems. Figure 1 shows the powertrain CAN-BUS on a late-model Volkswagen. You can see that the EPS control unit is just one part of the network of sensors and control units.

This connectivity has some serious advantages. The EPS module isn’t connected directly to the wheel speed sensors, but the ABS control unit is able to pass that data along on the BUS. It’s important to understand just how interconnected systems can be on modern vehicles.

Steering Angle Sensor

The steering angle sensor is arguably the most important sensor in the system; that’s why it’s first on the list. It is located between the steering column and the wheel, and, in many cases, is actually one part of a sensor cluster. This is due to the importance of the data it produces. A faulty steering angle sensor reading could mean the difference between making it around a corner, or colliding with another vehicle. Having multiple sensors onboard to measure the same thing offers built-in redundancy, and allows the control unit to confirm the data in real time.

Sensor operation will vary from one manufacturer to the next, so it’s best practice to always check the OEM service information before you start with diagnosis. Let’s look at a 2019 VW Golf Alltrack as an example. The sensor consists of two rings: the absolute (outer) ring, and the incremental (inner) ring. Each ring is divided into segments, which are read by a light barrier set (Figure 2). 

When looking at the data PIDs, you should see at least one steering angle sensor reading, measured in degrees. Sweep the steering wheel back and forth to confirm that the sensor is reading the change.

Steering Torque/Force Sensor

The second sensor on our list is the steering force sensor, also known as the steering torque sensor or steering moment sensor. This sensor is typically mounted on or inside the steering rack, and connected to the pinion gear (Figure 3). It is used to measure the amount of steering force that is being applied by the driver, then the control unit calculates how much steering assist force is needed, and applies it using the electric motor.

Again, sensor operation will vary from one manufacturer to the next, but we’ll use the 2019 VW Golf Alltrack again as an example. The steering input shaft and the pinion are connected by a torsion bar. A magnetic ring is affixed to the input shaft, and stators are affixed to the pinion (Figure 4). As the input shaft rotates, the torsion bar will twist, and the magnetic ring will move in relation to the stators (Figure 5). As a magnetic field is formed, the linear Hall sensors measure the electrical signal and calculate the amount of force being applied. 

When looking at the data PIDs, you’ll likely see two separate force/torque readings, measured in lb.-ft. or Nm. Turning the steering should cause these PIDs to rise.

Other Sensors

The EPS control unit monitors a number of additional sensors to ensure that the system operates efficiently, and doesn’t overheat. This includes, but is not limited to, the speed and power draw of the electric motor, the temperature of the control unit and electric motor, wheel speed, and the engine speed. All of these PIDs and more can be monitored by a scan tool, and can be invaluable when it comes time to diagnose an EPS system which is misbehaving.

Tips & Tricks

Needless to say, you’ll need a scan tool capable of bi-directional control for this type of work, a simple code reader won’t cut it here. You’ll need to scan the system for stored DTCs, then bring up the real-time data (PIDs) from the onboard sensors.

Check the OEM service information to see if there is updated software for the modules; this may clear up the customer concern. You’ll also want to familiarize yourself with how each of the sensors work on that particular application. Pay close attention to any service bulletins or notes from the manufacturer. This can save you (and your customer) some serious headaches!

The steering angle sensor needs to be reset or recalibrated whenever the battery has been disconnected, an alignment has been performed or the steering wheel has been removed. Be sure to get the wheels pointed straight ahead after an alignment is performed. If this isn’t done right, the system can be led to believe that the vehicle is drifting out of the lane, and could try to make an unnecessary correction. Follow the OEM service procedures to the letter, as failing to properly calibrate the sensors could lead to trouble down the road.