Axles are responsible for driving the wheels to move the vehicle. It’s not uncommon for drive axles to wear out or have leaking boots, requiring the boots or axle to be replaced. In states with safety inspections, a leaking axle boot can lead to the vehicle failing the inspection if axle grease is compromising the brake system. If your vehicle needs an axle, and you’re looking at how to replace it, how to replace the boots, and how much it costs, we have you covered in this article.

What Is An Axle?

Before we look at the repair and replacement cost of the front and/or rear axle on your car, it's worth understanding how this component works. There are different axle designs, but they serve the same purpose, which is to transfer power from the differential to the wheels. The axle type or design that is used on your vehicle will vary depending on the suspension and drivetrain configuration your vehicle has.

Front Axles

There are two types of axles found on the front of the vehicle. Constant Velocity (CV) joints are found on independent front suspension vehicles. Vehicles such as the Honda Civic and Nissan Sentra use CV joints in the front of the vehicle. U-joint axles - connecting a stub shaft to an axle shaft - are found in solid axle vehicles like the Ford F-250 and Jeep Wrangler.

Rear Axles

Like front axles, some vehicles will use a CV-style axle at the back; these are found in vehicles with an independent rear suspension. Other vehicles that utilize a solid axle will use a straight shaft design.

Stub Shaft Vs. CV Joint

Stub shafts are used on solid axle vehicles. The stub shaft connects to an axle shaft via a u-joint. U-joints are usually equipped with zerk fittings; these allow the joint to be greased to prolong the component's life. CV axles use an inner and outer joint connecting the CV stubs to the shaft that is sealed with rubber boots. The joints are typically not serviced like a u-joint, but the boots are often replaced.

Broken / Worn Axle Symptoms

Although broken axles are not regularly seen, it does happen. If the vehicle is equipped with an open differential (which allows the wheels to spin at different speeds when cornering) and an axle breaks, the vehicle will be rendered unmoveable. When axles wear, the joints begin to ‘click’ while turning. Additionally, if the CV axle outer boot tears, grease can leak onto the brakes. When brake pads become saturated in a grease-like fluid, the friction material breaks down and the rotors can become glazed. Both situations reduce the effectiveness of the braking system, resulting in a failed vehicle safety inspection. Other symptoms of a worn axle are vibrations or squeaks.

Lifting a vehicle with an independent front suspension can increase the CV axles wear due to the excessive driveline angle.

Can You Drive With A Broken Axle?

Most vehicles use an open differential. Therefore, if an axle breaks, the vehicle will most likely not be able to move as all the engine’s power will be transferred to the broken axle. If the axle is leaking, you’ll likely not notice until the joint becomes damaged. Axle grease is thick and will not leave a puddle like other fluids such as engine oil. Axle grease is more likely to stick on the surrounding components after it has been flung from the axle’s rotation. If your vehicle is 4WD or AWD, however, you can still drive the vehicle. We recommend replacing a CV axle as soon as possible.

A vehicle should not be operated in 4WD on dry pavement as differential or transfer case damage may occur.

How To Replace A CV Axle

Replacing a CV axle can be a challenging task depending on the vehicle make and model. Generally speaking, rear CV axles are more difficult to replace than front axles. Given that most mainstream vehicles are front-wheel drive, we’ll provide the steps to replace these.

The following tools are needed to replace a CV axle:

• Basic ratchet and socket set with assorted wrenches
• Axle nut socket set
• Pliers set
• Screwdriver set
• Ball peen hammer
• Plastic dead blow hammer
• 1/2-inch drive impact wrench
• 1/2-inch drive breaker bar
• 1/2-inch drive torque wrench
• Pry bar set
• Air hammer with assorted bits (punches can also be used)

These are some of the steps required to replace a CV axle:

1. Raise and support the vehicle.
2. Remove the relevant wheel.
3. Disconnect the lower ball joint.
4. Disconnect the brake line mounting bolt. (Do not remove the brake hose from the caliper)
5. Remove the axle nut cover and cotter pin. (if applicable)
6. Remove the axle nut.
7. Using an air hammer and a rounded pointed bit, push the axle through the hub assembly.
8. Use a pry bar to remove the axle from the transaxle.
9. Lube the inner CV splines and axle seal to prevent tearing of the seal. Carefully install the new axle into the transaxle by pushing the axle in by hand or with a plastic dead blow hammer.
10. Position the outer splines through the hub.
11. Reconnect the brake line and ball joint.
12. Torque the axle nut to spec using the torque wrench.
13. Reinstall wheel and torque lug nuts.

How Much Does It Cost To Replace An Axle?

Given the variances between vehicles and axle designs, the cost of a car axle replacement will vary. RepairPal estimates that the average car axle shaft replacement cost will be between $850 and $1,000. A similar figure can be expected for rear axle replacement costs. A new CV axle will cost roughly $1,000 to $1,200. Aftermarket CV axles are significantly cheaper than OEM axles from the manufacturer, costing between $60 and $300. Most aftermarket axles will come with a decent limited lifetime warranty. Typically, these warranties won’t reimburse the labor time. Fortunately, most CV axle labor times are between 1 and 2.5 hours. New OEM axles will cost anywhere between $500 and $1,000, so if you elect to use an aftermarket axle, you can bring the average cost from $1,000 down to $300 to $500. You can save even more if you do the job yourself.

Replacement boots cost between $50 and $120 but come with increased labor times. The average cost to repair a CV joint or axle boot is between $200 and $350. It may be more cost-effective to replace the axle with a quality aftermarket part rather than replace the torn boots.

Although the cost of a broken axle repair can be high, it can leave your vehicle immobile and a torn outer axle boot can compromise your brake system; both scenaros are risky. The manufacturers' service manuals state an axle should be replaced after a boot has been torn as the joint will experience premature wear from contamination without being sealed with the proper lubrication. For these reasons, we recommend replacing a worn or broken CV axle as soon as possible.

Try to park your vehicle with the wheels positioned straight ahead to prolong axle boot life.