MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
Last updated:
In this guide (5 sections)
Mercedes-Benz front differential bearings may fail on vehicles equipped with 4Matic. If this does happen, it will cause horrendous noise from the front of the vehicle. The noise is most noticeable when coasting or decelerating. The noise intensifies at higher speeds. Other symptoms of a bad Mercedes front differential include.
- A howl or whine during acceleration
- Whirring noise only while decelerating is often caused by a bad pinion bearing
- Rumbling or humming noise at low speeds is often caused by worn carrier bearings.
You would think a differential would last at least 300,000 miles or more, right? Unfortunately, we have seen a few cases where a differential failed under 100k miles. 2006-2012 models, such as the ML, GL, and R class, have a higher-than-average failure rate of front differentials.
Rebuilding Mercedes Front Differential
To verify the source of the noise, have a mechanic lift the vehicle on a garage lift and have the engine running. While all wheels are off the ground, place the car in Drive and get the wheels spinning. Listen for noise coming from the front differential. The noise originates from the center of the vehicle. Also described as a “rrrrrrrrrr” noise from the front end. The noise gets more noticeable when you increase the wheel’s rotational speed.
Before anyone does this: a vehicle running in Drive with all four wheels spinning is the most dangerous part of this whole job. It belongs on a proper garage lift with the car secured on the lift arms, never on jack stands or a floor jack. Keep everyone clear of the spinning wheels and out from under the car while it is in gear, and have one person stay at the driver’s seat the entire time.
We have seen cases where a mechanic diagnoses the noise as a bad front wheel bearing. While the noise coming from a bad front differential bearing sounds similar to that of a bad differential wheel bearing, a differential bearing noise comes from the center of the vehicle.
How to rebuild the Mercedes-Benz differential
Front differential issues are common among 4Matic models and are quite common in the 2006-2012 Mercedes W164 (ML), X164 (GL), and W251 (R) classes. The differential and bearings are the same in all these models.
A Mercedes-Benz differential replacement at the dealership and auto repair shops typically runs in the $4000-$6500 range. That’s because your dealer and most shops will not repair your differentials. We have not heard of any Mercedes-Benz dealers repairing these units by changing the failed differential bearings, which are often the culprit. The good news is that you can rebuild your bad Mercedes-Benz differential if you have the right tools and reasonable DIY skills. The two carrier bearings frequently fail (a common problem on GL, ML, R, GLK class, and even some Jeep models) but can be replaced once the differential is out, provided you have a bearing puller and a press, since the carrier bearings are a press fit.
You will need the Mercedes Differential Bearing Kit to rebuild the Mercedes-Benz front differential.
Watch this short video we posted on YOUCANIC. We explain what needs to be replaced.
Mercedes Differential Bearing Kit
New bearings for the Mercedes-Benz front differential cost between $200 and $300 when purchased online. At the time of this posting, the dealer did not sell the bearings. The only parts you can purchase from the dealer are the seals and rubber bushings for your differential.
We recommend changing the seals and the bushings for the differential if you plan on changing the bearings. There are three seals and three bushings. Those parts can be purchased from the dealer. If they fail later, you must remove the differential, which is time-consuming.
You will need a few essential tools plus a Mercedes Differential Bearing Kit and 1L of 75W-85 synthetic gear oil.
Photo Gallery
Below, you will find a few pictures we took during this repair.
Will a Scanner Find a Bad Front Differential?
Not directly, and that is worth saying plainly before anyone buys a tool expecting it to. Nothing inside the differential reports to a control unit, so a worn carrier bearing sets no fault code. The diagnosis is the one described above: the car on a lift, the wheels turning, and your ears.
Where a scan earns its place on this job is before you commit to it. Pulling a front differential on a 4MATIC is a long day, so it is worth confirming the car is not storing faults elsewhere in the driveline first, rather than rebuilding a differential to chase a noise coming from something that does report. A full system scanner such as the YOUCANIC UCAN-II Pro reads the modules a basic code reader cannot, which is what lets you rule the rest of the driveline out.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
