What Does It Mean When My CV Axles Boots Are Leaking?

By Karen Johnston December 2, 2011

Quick facts

CV axles transfer power from the transmission to the wheels while accommodating suspension movement.
A cracked boot lets grease escape and allows dirt and moisture into the joint.
Once contamination reaches the joint, the entire axle typically requires replacement.
Clicking during turns is the most recognizable symptom of a worn outer CV joint.

What is the CV joint axle?

The constant velocity joint (CV) axles transfer power from the transmission or differentials to a vehicle's wheels. These components also provide the flexibility needed for turning and navigating road obstacles. Front-wheel drive, all-wheel drive, and some rear-wheel drive vehicles with independent suspension use CV joint axles.

Parts of the CV joint

CV joints contain bearings and cages that enable rotation and power delivery at various angles while allowing the axle to change length during suspension movement. A protective layer of grease keeps these components lubricated, contained within a flexible rubber boot. Once the boot cracks or tears, the protective grease needed to keep the constant velocity joint lubricated will leak its way out, then moisture and dirt will work their way in. When contamination occurs, replacing the entire axle becomes necessary rather than just the boot.

Signs of a failing CV joint axle

Watch for these warning indicators:

Clicking or popping sounds during turns. This is the most common symptom and usually means the outer CV joint is worn
Metallic cracking or clunking noises during acceleration or deceleration, which points to inner joint wear
Grease splattered on the inside of the wheel or along the axle, a torn boot throwing grease as the axle spins
Vibration that increases with vehicle speed

Complete failure renders the vehicle immobile since power cannot reach the wheels.

If you notice grease splattered on the inside of a wheel or hear clicking in turns, have your trusted repair facility inspect the CV boots at your next service. Catching a torn boot early, before contamination reaches the joint, can save the cost of a full axle replacement.

Happy Motoring!

Frequently asked questions

Common questions

How long can I drive on a torn CV boot before the joint is damaged?

There is no reliable answer because it depends on conditions. In a clean, dry environment a torn boot may allow the joint to run for weeks or months before contamination causes noticeable wear. In wet, muddy, or sandy conditions, dirt and grit enter the joint immediately and grinding begins much faster. The safest approach is to have the boot addressed as soon as grease splatter or a torn boot is identified. The cost difference between a boot repair and a full axle replacement is significant.

Can a CV boot be repaired without replacing the whole axle?

If the boot is caught early and the joint itself is still in good condition, some shops will replace just the boot and repack the joint with grease. However, many shops recommend replacing the entire remanufactured axle shaft instead, because it is often not much more expensive and eliminates the risk of the joint failing shortly after the boot repair. The decision depends on the axle's mileage and the condition of the joint on inspection.

Do all-wheel drive vehicles have more CV joints to worry about?

Yes. A front-wheel drive vehicle has two front CV axles, each with an inner and outer joint, four joints total. An all-wheel drive vehicle adds rear axles with their own inner and outer joints, doubling the number of boots and joints that need monitoring. The rear boots on AWD vehicles are often overlooked during routine inspections because they are less visible, so it is worth specifically asking for a CV boot inspection on all four corners.

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