Benz Tips · TransmissionTransmission service, the whole driveline

Which transmission does your Mercedes have?

Modern Mercedes-Benz models use a few different automatic transmissions. Each one is built for either rear-wheel drive or front-wheel drive, and each one has its own service needs:

Not sure which one you have? Give us your VIN and we'll tell you in a minute.

When is a Mercedes transmission service due?

We'll start reminding you around 50,000 miles, so it's on your radar before it's due and the cost isn't a surprise. Most transmission services take 2–3 hours, and we can do yours at the same visit as your yearly service.

What happens if you skip it

Mercedes transmissions really like to be serviced every 60,000 miles. Here's what we see when they're not:

1. Past 60,000 miles: shifts start to feel harsher than you remember from when the car was new.
2. Around 80,000 to 100,000 miles: problems start to show up. It can shake or shimmy at times, and the harsh shifting gets worse.
3. Around 120,000 miles, never serviced: we often see failures that can't be repaired. The transmission has to be replaced.

This is the part we reset. During a transmission adaptation, we use XENTRY to change how the transmission computer engages the torque converter. That helps smooth out the shifts.

Compared with that, a $600–$1,100 service every 60,000 miles is the smart money.

What a complete transmission service includes

• Fluid: drained and refilled with factory-certified Mercedes fluid only.
• A new filter
• A new pan seal
• A new drain plug
• New aluminum pan bolts, every time

Why factory fluid? Some lower-priced fluids can make a Mercedes transmission shift harsh or start to shimmy. Factory-certified fluid keeps the shift quality the car was built with.

Transmission adaptation: smoothing out the shift

With every service we'll talk to you about a transmission adaptation. Using XENTRY, the factory Mercedes-Benz diagnostic system, we reset how the torque converter applies and how each shift feels. Then we road test the car to teach the transmission its new settings.

• When a transmission has gone a long time without service and has started to shake or shimmy, an adaptation can smooth it out.
• Sometimes it doesn't help. That usually means there's damage inside the transmission from the lack of service. At that point, you can keep driving it as it is, or replace the transmission.

The 9G-TRONIC (725) needs special tools

Most 2016-and-newer Mercedes have the 725 transmission, the 9G-TRONIC. It's much less forgiving about fluid level than the older 722.6 and 722.9. Just 2 millimeters of difference in fluid height can cause shifting problems.

• Setting the level right takes a Mercedes XENTRY unit and a $1,500 ultrasonic sensor.
• The old-school drain-and-fill method is fine on a 722.6 or 722.9, but not on a 725. Without XENTRY and the sensor, it isn't a proper service. Keep that in mind when you choose where to take your Mercedes.
• The 725 service costs more, $900–$1,100. Its filter is built into the transmission pan, so you're buying a new pan and filter, not just a filter. The fluid also costs almost twice as much.

We do our best to keep these services affordable, so your Mercedes stays in good shape for a long time.

4MATIC: service the transfer case with the transmission

If your Mercedes has 4MATIC all-wheel drive, it has a transfer case. It's the extra unit on the back of the transmission that splits power between the front and rear wheels, and it has its own fluid.

• The transfer case fluid needs to be changed every 60,000 miles (AMG: 40,000), the same as the transmission.
• Skip it, and the fluid breaks down or leaks out. The internal chain stretches, and you'll hear a loud pop when you accelerate.
• At that point the whole transfer case has to be replaced.

Front and rear differentials

The differentials send power to the wheels on each axle. They need fresh fluid too, just less often:

Not every Mercedes has every part:

• Front-wheel drive: a front differential only. No rear differential, no transfer case.
• Rear-wheel drive: a rear differential only.
• 4MATIC: all three: a transfer case, a front differential and a rear differential.

Many shops only sell the transmission service. It's what everyone knows, and it's the fastest and easiest job. The transfer case and differentials take more time, but they're all part of the same driveline, so we look at them together.

CLA and GLA: why the rear diff needs service every 30,000 miles

The rear differential on a CLA or GLA 4MATIC isn't just gears. It has an electronic locking clutch built in that controls when the rear wheels lock and engage. That's what sends power to the rear wheels when the car needs it.

This clutch commonly fails when the rear differential isn't serviced every 30,000 miles. Here's how it usually goes:

1. You feel a thumping and shaking from the rear of the car.
2. Then the 4MATIC warning light comes on, telling you the 4MATIC system isn't working.
3. At that point the rear differential has to be rebuilt, usually $1,200–$1,800.

Don't know when it was last done?

A service history is very helpful, but don't worry if you don't have one. We'll help you find out:

• During the service we look at the color and condition of the fluid, and the pan and seal. Our trained technicians can tell whether it's been done in a reasonable amount of time. No guessing.
• We can check Carfax.
• We can call the dealership and get a printout of the work done under your factory warranty, in most cases.

What does it cost?

Compare that with $1,200–$1,800 to rebuild a CLA or GLA rear differential, or $6,000–$9,000 for a rebuilt transmission with a new torque converter. Your exact price depends on the model, and we confirm it with you before any work starts. Call with any questions about your transmission or its related services.

Common questions