Mercedes A-Class, B-Class Common Gearbox Problems

The Mercedes A-Class and B-Class have long been favourites for those who appreciate a blend of style, performance, and practicality. Both models offer a choice between a 5-/6-speed manual gearbox for those who enjoy a more hands-on driving experience and an automatic version with a CVT or 7-speed DCT gearbox for seamless, effortless cruising. The A-Class, with its sleek design and compact dimensions, is perfect for urban adventures, while the B-Class provides a bit more space, making it ideal for families or those who need extra room. Inside, you’ll find a well-crafted cabin with intuitive technology and premium materials, ensuring every journey is as comfortable as it is enjoyable. Whether you prefer the engaging manual or the smooth automatic, both models deliver the refined driving experience Mercedes is renowned for

Mercedes (A-Class, B-Class) CVT / 7-speed DCT Faults & Repairs Common Problems

The Mercedes A-Class and B-Class models equipped with the CVT or 7-speed DCT gearbox have encountered several common issues. These problems can impact the driving experience and may necessitate intervention from a qualified technician. Below is a list of the most frequently reported issues:

• Clunk or Noise When Shifting into P, N, or R – Often described as a “massive thud,” this issue is unsettling and worsens in cold conditions, affecting all models with 7G DCT.
• Delayed or Rough Gear Changes – The transmission may shift roughly or take longer than expected, leading to jerkiness and reduced performance, common across A-Class and CLA models.
• Issues with Creeping Forward on Uphill Slopes – Cars may delay moving forward on inclines, posing safety risks, especially in models with hill start assist like GLA and A-Class.
• Incorrect Oil Level – Even a small variation in oil level can cause shift quality issues, with maintenance neglect being a key factor across all models.
• Flywheel Failure – Dual-mass flywheel failures can lead to metal shavings damaging the transmission, causing power loss, particularly in certain A-Class variants.
• Transmission in Limp Mode – Often due to internal ECU failures, this mode restricts performance, commonly affecting Mercedes A-Class models with the 722.8 transmission.
• Loss of Power – A compromised ECU can lead to significant power loss, often accompanied by a “Transmission Visit Workshop” warning message on the dashboard.
• Not Selecting Gears – The transmission may fail to select gears, often due to speed sensor faults, affecting A-Class and B-Class models with CVT.
• Sticking in Gear – Gearbox may stick in a particular gear, often linked to output speed sensor faults, impacting driving experience in affected models.
• Speed Sensor Fault – Faulty speed sensors can lead to implausible RPM signals, causing transmission issues, particularly in models with the 722.8 CVT.

Mercedes (A-Class, B-Class) 5-/6-speed Manual Faults & Repairs Common Problems

Owners of the Mercedes A-Class and B-Class with the 5-/6-speed manual gearbox have reported several common issues. These problems can affect the driving experience and may require attention from a qualified technician. Below is a list of the most frequently encountered issues:

• Clutch Slippage – Occurs when the clutch fails to fully engage, leading to a loss of power transfer and increased engine RPMs without corresponding acceleration.
• Gear Grinding – Caused by worn synchronizers or improper clutch engagement, resulting in a harsh noise when shifting gears.
• Stuck Gear – The gear lever becomes difficult to move, often due to linkage issues or internal transmission damage.
• Difficulty Engaging First Gear – Often due to worn synchronizers or clutch issues, making it hard to start from a stop.
• Transmission Fluid Leaks – Leaks can lead to low fluid levels, causing poor lubrication and potential damage to transmission components.
• Worn Synchronizers – Lead to difficulty in shifting smoothly between gears, often accompanied by grinding noises.
• Clutch Pedal Issues – A soft or spongy pedal feel can indicate air in the hydraulic system or a failing master/slave cylinder.
• Transmission Noise – Unusual noises such as whining or clunking can indicate internal wear or damage to gears and bearings.
• Gear Popping Out – The transmission unexpectedly shifts out of gear, often due to worn gear teeth or linkage problems.
• Hard Shifting – Difficulty moving the gear lever, often caused by worn linkage components or insufficient lubrication.

Common Mercedes A-Class, B-Class Gearbox Issues

If your vehicle is experiencing any of the below symptoms, it is highly recommended to have your vehicle diagnosed before it causes further damage internally or to other components within the gearbox system.

• Unable to select gears / drive / reverse
• Jerking in gears / dropping out of gears
• Burning smell from gearbox/clutches
• The gearbox warning light illuminated on the dashboard
• Whining / crunching / humming noises
• TCM / Mechatronic error codes

Mercedes A-Class, B-Class Gearbox Repair Benefits

We offer customers a range of benefits when it comes to repairing their gearboxes. With cost-effective repair services, our team of highly skilled technicians are well-versed in repairing various types of gearboxes, making them capable of handling repairs for all makes and models.

Low cost Save up to 60% off main dealer prices with repairs, rebuilds, and reconditioning.	All makes & models Automatic, CVT, DSG, S-Tronic, Powershift, ZF and many more automatic types repaired.
Skilled technicians Our team is highly skilled and has experience with repairs on almost every type of automatic gearbox.	Warranty Provided All types of repair come with a 12-month / 12,000-mile warranty.

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