Many 4-wheel-drive owners have reported hearing a loud “clicking” noise when in 4WD mode. The problem only seems to manifest itself when the vehicle is under load or while turning and braking or under acceleration. The strange ‘clicking’ or ‘clacking’ noises are only heard when 4WD is engaged and not in 2H or 2-wheel-drive mode. The ominous noise seems to be in sync with the wheel speed. What could be the cause of this ‘clicking’ or ‘clicking’ noise when in 4 wheel drive?
When hearing a clicking or ‘clanking’ metal sound only when 4 wheel drive is engaged and under load or acceleration around corners is a sign associated with CV joints. CV joints are Constant-velocity joints (also known as homo-kinetic or CV joints) that allow a drive shaft to transmit power through an adaptable angle to the wheel, at constant rotating speeds, without any noticeable increase in friction or play. One of the most common and most noticeable symptoms of a bad or failing CV joint is an audible clicking noise when turning.
But what causes this phenomenon to occur and is it dangerous to drive your vehicle in this state? Let’s look at what can be done to rectify it and what costs are involved to replace it. The following article will discuss the causes of CV joint failures and the possible solution.
How Do You Break a CV Joint
The CV axle assembly consists of two CV joints on either end of a drive shaft (an inner joint and an outer joint). The axle assembly seldom fails but rather the CV joints themselves. In most cases, it is the outer CV joint that fails first since it does more work than the inner CV.
Excessive Force When in 4WD
A CV joint failure can happen when 4WD is engaged and the front wheel of your vehicle becomes airborne in a cross axle or rock climbing situation. If the driver accelerates aggressively and the airborne front wheel hits the ground while spinning fast, is when the CV joint is most likely to get damaged or fail. The immense torque sent to that spinning wheel combined with the intense forces that are transferred through that wheel shaft can be too high for the CV joint bearings to handle once the spinning wheel suddenly meets a high resistance surface. I.e. when it makes contact with the ground or dry rock surface again. The airborne front wheel will receive all the available power since torque is always transferred to the wheel with the least resistance. In this instance, the airborne wheel.
Torn CV Boot
A second scenario of how a CV joint can fail is due to a lack of lubrication. This can be caused by a brittle or torn CV boot cover. That is the rubber cover that is connected to the CV joint casing to retain all the grease inside the boot and keep the bearings well lubricated and free of grit and dust. Once that boot tears and all the grease runs out is when the CV becomes vulnerable. It only takes a few grains of sand or dust to get inside the CV joint to cause wear and eventually failure. This accompanied by a lack of lubrication is another cause of the ‘clicking’ or ‘clucking’ noise you hear when the CV is dry and worn out.
Old Age
A third way a CV joint can fail is when the rubber boot becomes old and brittle due to age and wear. Road or off-road track debris can damage the rubber cover, causing the grease that is meant to keep the joint lubricated to leak out of the joint.
All it takes is for some dirt, moisture, or grime to enter that CV joint, and it will fail sooner rather than later.
Extreme Suspension Upgrades and Body lifts
When you upgrade the suspension of your 4WD most people seldom consider the implications it will have on the CV joints. Especially extreme lifts of 50mm and above on certain Utes. The angle that the axle shaft needs to rotate at is extended and this is when small tolerances give way to more space opening up between the moving parts of the joint. As space between the parts increases the parts begin to thump against each other and within a short period of time they fail.
Handling Symptoms of a Failed CV
A few signs and symptoms occur when you have a failing CV joint. These symptoms are the following:
- Clicking sounds that are in sync with the wheel speed
- The popping and grinding noises
- Loud clacking noises when you turn under full lock
- Later loud clacking sounds can become really bad even under partial lock.
- A vibration that is felt in the steering wheel
- A vibration that is prominent in the floorboard of the vehicle
How To Inspect Your CV Joints
You need to regularly inspect the condition of your CV joints. There are a few methods you can apply to determine the state of your CV joints.
Visual Inspection
This method requires your vehicle to be parked on a flat-level surface first. Park the vehicle and stand directly in front of the vehicle and bend down till you can visually see both CV axle shafts. Check to see if both left and right front axle shafts are at the same angle.
Do a visual inspection of the rubber boots. Inspect for cracks and leaks on the boots. Look for loose or missing clamps. These are all vulnerable low-hanging components that can easily pick up a branch and tear open a rubber boot without even making a sound.
Slide Underneath
If you can park the vehicle on a hoist or jack the front of the vehicle up so you can get underneath, physically grab the CV axle shaft and give it a few pushes and pulls. There should be minimal play on the axle shaft. If the play exceeds 1/8 inch in any direction the CV is worn.
Why only in 4WD mode
The clacking sound usually manifests itself when non-permanent vehicles engage in 4WD mode. This is because part-time four-wheel-drive trucks are usually driven in the 2H mode in the city and on high-traction tar roads. When in 2H the front axle is disengaged and it is only the rear driveshaft that is propelling the vehicle forward. The front driveshafts and wheels are not propelling the vehicle forward but simply coast along, hence the driver not hearing any dubious clicking sounds in 2H but only when the 4H mode is engaged.
How to tell which is the bad CV Joint
The easiest method of detecting the bad CV is to drive the vehicle with the 4H mode selected for a short while. Get to a grassy patch or a gravel road before you engage 4×4 in a non-permanent 4-wheel-drive. Once you have the vehicle in 4H lock the steering to the left and drive forward. If the left front wheel is making the clacking or clicking sound, bingo! Do the same exercise for the right side.
Inner CV Joint
If you notice a heavy vibration on the steering and a slight whining sound coming from more the center of the vehicle, you might have to have your inner CV joint inspected. Take your 4WD to a reputable brake and suspension center to have them professionally inspected and tested.
Can you drive with a Bad CV joint
In order for the CV joint to function efficiently, it needs lubrication, as well as protection from dirt, dust, and other debris. Once the boot that seals the CV joint is damaged, the grease leaks out and contamination begins to set in, eventually causing the CV joint to wear out and fail.
Conclusion
When you drive a 4-wheel-drive vehicle and regularly do off-road trails and rough tracks you will need to inspect your CV joints after every outing. If the CV fails on a 4×4 trail you will definitely hear the snapping sound and you will experience diminished off-road capability.
After a day out thoroughly inspect the rubber boots to ensure they are still intact and firmly secured with all the grease inside. Replacing a torn CV Boot is much cheaper than a failed CV joint so it pays off to do the inspections regularly.
When hearing a clicking or clunking sound when in 4H, rather disengage 4WD mode and drive slower in 2H until you can get to a service center or mechanic to have it replaced.