In this guide, you will find instructions on how to replace the Mercedes-Benz front axle, CV joint, and boot.
This guide applies to Mercedes-Benz 4Matic vehicles including C, E, S, ML, GL, GLA, GLE, GLS Class. Pictures shown below are from a 2016 Mercedes-Benz C300 4Matic.
What will you need?
- Mercedes half shaft
- Mechanic Toolset Metric
- 21mm wrench
- 27mm hex nut socket or 32mm bi-hex socket
- Jack and jack-stand
- Breaker bar
- Pry bar
- Ball joint removal tool
- Penetrating oil
How to replace the front CV axle on a Mercedes-Benz.
- Park vehicle on level ground and apply the parking brake to prevent vehicle movement.
- Break loose the lug nuts but do not remove them yet.
- While the car is still on the ground, remove the center cap with the Mercedes-Benz logo from the wheel. This will expose the center axle shaft bolt. (Shown with the wheel removed.)
- Using a breaker bar and an appropriate socket, break loose and partially unbolt the center axle shaft bolt. Depending on the model, you will need either 27mm hex or 32 bi-hex sockets. For this step, you will need a breaker bar and plenty of force.
- Jack up your car and rest it securely on jack stands.
- Unbolt the wheel lugs and remove the wheel.
- Separate the front lower control arm or the upper control arm, depending on the model. You want to disconnect the control arm that will allow the steering knuckle to move out. In this case, we disconnected the upper control arm. To separate the control arms use a ball joint puller to damage the ball joint boot.
- On most models, you will need to detach the stabilizer bar link rod from the stabilizer bar.
- Pull out the hub carrier, as far as the CV joint allows. Then tap on the center axle shaft bolt with a hammer. This will break free the CV joint out of the wheel hub. Now you can move the hub carrier out of the way.
- In some cases, you might need to remove the brake caliper to gain better access.
- Remove the lower engine splash shield held in place with several 8mm screws and note the inner CV joint on the front transfer case.
- Using a pry bar as an extension tool and a hammer, tap the inner CV joint out of the transfer box case.
- Visually check if for traces of oil on the transfer case. If there are any, you will need to replace the shaft seal.
- Clean out the splines in the transfer box case and the hub carrier with a brake cleaner. Also, if suspension parts have traces of grease, clean them out as well.
- Slide in a new half shaft, and push the inner joint into the transfer box case. You might need to wiggle it around until it snaps in. Make sure it is all the way in.
Constant velocity joints, also known as CV joints, transfer the transfer case to the wheels.
On a Mercedes-Benz with rear-wheel drive, you won't have a CV joint unless you have a 4Matic Mercedes-Benz.
- If you can't break loose the center axle bolt, remember that you need to turn the bolt counterclockwise to remove it.
- It is not recommended to remove the axle bolt while the wheel is off, as this can put too much strain on the transmission and transfer case.
- Suspension parts are exposed to dirt, salt, water, and other contaminants. This means that bolts that hold them together might be corroded and extremely heavy to unbolt. It is good to spray them with penetrating oil and leave it for 15-30 minutes before trying to unlock them.
- While working on the suspension, visually check all parts. Ball joints have rubber boots for protection. As with CV rubber boots, the ball joint must be replaced if the rubber boots are damaged.
- Most CV joints should have a retaining ring at the end of the inner CV joint spline.
- You will need to rotate the half shaft until the tabs on the case align with grooves on retaining rings. Usually, there are no markings, so you have to try until you get it right.
- If you have a cracked Mercedes CV boot, you need to remove the CV joint. Use instructions in this guide to remove the CV joint. Then separate the CV joint from the axle to replace the CV boot.
- On vehicles with air suspension, you should charge the air spring before lowering the vehicle.
- Most models are more practical and change the whole half shaft, as it is faster and easier. And it is cheaper, as buying CV joints and new Mercedes CV boots separately.
Mercedes CV boots are known to fail quite frequently. If a damaged Mercedes CV boot is not noticed on time, it will cause the CV joint to fail.
Replacing a Mercedes CV boot or CV joint requires the removal of the front axle.
- Clicking noise when moving from a standstill
- Grease on the inner tire edge of the wheel well
- Vibrations while driving
- Knocking sound when going over bumps
Frequently Asked Questions
Center axle bolt tightening torque
As tightening torque values vary both on the model and yearly basis, it is best to verify by calling the dealer.
Axle bolt socket size
In most cases, you will need a 27mm hex nut socket. However, some models might have a larger 32mm nut, so that you will need a 32mm bi-hex socket.
What is the easiest way to diagnose a bad CV joint?
Find an empty parking lot with enough place to drive in circles safely. While standing still, turn the wheel all the way to one side. Put your car into gear and accelerate fast. Listen for loud clicking noises, then do the same driving in reverse.
Repeat the whole procedure with the wheel turned all the way to the other side.
How can I prevent CV joints from failing?
Visually inspect your CV boots for cracks, tears, or traces of grease.
CV joints are lubricated by grease and have rubber boots that protect them from dirt and debris. When the rubber boot cracks or tears open, grease will be forced out of the CV joint while driving. This will leave the CV joint without proper lubrication. To make things worse, dirt and other contaminants will only speed up the wear process.
Can I drive my Mercedes with a bad CV joint?
Driving around for a long time with a badly worn CV joint is not safe. In extreme cases, it can break without any prior warning signs. If this happens while driving or accelerating, it might severely damage suspension components.
Still, this doesn't mean that you must stop using your car at once. You can drive it for a shorter period of time as long as you adjust your driving style. Avoid hard acceleration and be extra gentle with the throttle when turning. Replace the bad CV joint as soon as possible.
Are the traces of oil on the transfer case caused by a bad CV joint?
If you see traces of oil on your transfer case, this means that a shaft seal is bad. You will need to replace it before installing a new half-shaft.
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