This guide is helpful if you are trying to learn how to:
- replace Mercedes-Benz front axle
- change Mercedes CV joint
- replace Mercedes CV 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.
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.
Symptoms of Bad Mercedes CV Joint
- Clicking noise when moving from stand still
- Grease on the inner tire edge or wheel well
- Vibrations while driving
- Knocking sound when going over bumps
What will you need?
- Mercedes half shaft
- 1/2" Socket set
- 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 Mercedes front axle and CV joint
On most models, it is more practical and to 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.
- First apply your parking brake to prevent vehicle movement. While the car is still on the ground, remove the wheel center cap. This will expose the center axle shaft bolt.
- 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 socket. In most cases, you will need to step on the breaker bar handle, using your body mass to loosen up the bolt.
- Before jacking up the car, loosen the wheel lug nut with a wheel wrench. Do not remove the lug nuts. 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 the most. In this case we disconnected the upper control arm. To separate the control arms use a ball joint puller so that you don't damage the ball joint boot.
TIP: Did you know that you can borrow auto repair tools from many local parts stores such as Autozone, Advance Auto Parts or O'Rilley?
- On most models, you will need to detach stabilizer bar link rod from stabilizer bar.
- Pull out the hub carrier out , 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.
- Although not necessary on most models, in some cases you might need to remove the brake caliper to gain better access. Remove the lower engine compartment paneling.
- Using a pry bar as a extension tool and a hammer, tap the inner CV joint out of the transfer box case. If it doesn't come out with a light tap, turn the half shaft back and forth (see tips & tricks).
- 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 in 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 power from the transfer case to the wheels. Car owners that have been driving front wheel drive cars most of their life usually are familiar with bad CV joints. CV joints are one of the weak points for this type of drive train.
Rear wheel drive cars have CV joints as well but rear CV joints don’t fail as often. If you have been driving a Mercedes for most of your life, chances are that you have never heard about CV joints since the majority of Mercedes-Benz vehicles are rear wheel drive.
Unless you have a 4Matic Mercedes-Benz. These models have active front wheel drive which means they have CV joints at the front wheels.
- If you can't break loose the center axle bolt, remember that you need to turn the bolt counterclockwise to unbolt it.
- It is not recommended to remove the axle bolt while the wheel is off, as this can put to much strain in 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 a good idea 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, ball joint must be replaced if the rubber boots are damaged.
- Most CV joints should have a retaining ring on 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 just 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 CV joint from axle to replace the CV boot.
- On vehicles with air suspention, you should charge the air spring before lowering the vehicle.
Mercedes CV Joint Replacement Cost
Average cost to change Mercedes-Benz CV joint at the dealer ranges between $850 - $1200. The reason that it is so expensive is because Mercedes-Benz dealers (typically) don't replace only the CV joint or the boot. They recommend replacing the whole front CV half shaft assembly.
If Mercedes shop replaces your CV half shaft, expect to pay between $480 and $800.
If you decide to tackle the job yourself expect to spend between $80 and $200. Assuming you have the tools. If you catch the problem early enough you may be able to get aay with simply replacing your Mercedes CV boots which will cost you between $50 and $100 for new boots.
Replacing Mercedes front axle or CV boot is labor extensive. Plan on at least three hours.
Frequently Asked Questions
Center axle bolt tightening torque
As tightening torque values vary both on model and year 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 you will need 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. Than do the same driving in reverse.
Repeat the whole procedure with 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 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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