S tronic 0B5 Problems: Mechatronic, Clutches and Oil

The 7-speed S tronic 0B5, also known as the DL501, is a longitudinal gearbox you'll find in the A4 B8, A5, A6 C7, A7 and Q5 with 2.0 TFSI, 2.0 TDI and 3.0 TDI engines. It's built to handle plenty of torque and has two wet clutches that run in oil. Look after it and it's a lovely gearbox. But here's the catch! Skip the servicing and one day it could land you with a very expensive repair. That's why I want you to understand S tronic 0B5 problems before they catch you out.

What's different about the S tronic 0B5?

I've explained this before in my A4 B8 service schedule, but it's worth going over again because it's important. The S tronic 0B5 uses two separate oils. One is at the front, where the clutches and mechatronic unit sit. The mechatronic is the brain of the gearbox. The other oil is at the back, where the gears and differential are. They're different oils and need changing separately. And here's where things go wrong. Plenty of garages change just one oil and tell you the gearbox has been serviced. But it hasn't.

What are the signs of S tronic 0B5 problems?

• You feel a thump when the gearbox changes gear, especially at low speeds or when you're slowing down at traffic lights.
• The gearbox jerks or judders when you pull away.
• A gearbox warning light comes on and the gearbox goes into limp mode.
• The car will only drive in even gears or odd gears.
• You suddenly lose reverse gear.

When we read the fault codes, we often find a problem with the hydraulic pressure or the sensors that monitor clutch movement. But there's something you need to understand. A fault code tells us where the gearbox has noticed something wrong, not necessarily which part has failed. Our job is to find the actual cause.

Is it the mechatronic unit or the clutches?

That's the first thing we need to work out. At Das Auto Service, we start with diagnostics, not by ordering parts. We check the gearbox's live data: pressure, temperature, how much each clutch is slipping and the adaptation values. This tells us whether the clutches are worn, the mechatronic unit is losing pressure or a sensor is giving us false readings. I don't want you paying for parts on a guess.

• If the clutches are worn out and have reached the end of their life, we replace the clutch pack and carry out the adaptation.
• If the mechatronic unit can't maintain the required pressure or its electronics have failed, we replace it with a new one.
• If a sensor is causing the trouble, sometimes the fix is much simpler than replacing the entire mechatronic unit.

Why is the oil so important in an S tronic?

In an S tronic, the oil does much more than lubricate. It cools the clutches and helps the mechatronic unit do its job. Over time, the clutches wear and release friction material into the oil. Leave the oil change too long and those particles pass through the valves, wearing them down like sandpaper. That's why I recommend changing both oils every 60,000 km, using genuine oils and service parts. If you use alternatives, the interval is much shorter. This really isn't the place to save a few pounds.

How can you protect your S tronic 0B5?

• Change both oils on time. Always use genuine oils and filters.
• Don't hold the car on a hill using the accelerator. That's what your brakes are for.
• In heavy traffic, don't keep letting the car creep forward with your foot lightly on the brake. Either stop properly or move off.
• If you notice the gearbox starting to thump, vibrate or judder, bring it in and let us check it. Don't wait for it to turn into something more serious.

Advice from Kris Mladenov: For me, regularly changing both oils in the S tronic 0B5 is the best insurance against a major repair. A mechatronic unit or clutch pack can cost as much as years of proper gearbox servicing. And it all starts with the oil.

I hope you've now got a better idea of how the S tronic 0B5 in your Audi works and why I'm so particular about servicing it properly. If this article has helped you, send it to a friend who drives an S tronic too. You might save them a lot of headaches.

The solution in our shop

S tronic 0B5 mechatronic unit for Audi A4, A5, A6, A7 and Q5

Mechatronic unit for the S tronic 0B5 in the A4, A5, A6, A7 and Q5. For when diagnostics have confirmed that the original unit can't be repaired.

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S tronic 0B5 clutch kit

Clutch kit for the S tronic 0B5. For when both clutches are worn out and need replacing.

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Genuine gearbox service kit for Audi S tronic automatic gearboxes

Genuine S tronic service kit with oils, filters and seals.

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Genuine G052529A2 1-litre gearbox oil for S tronic dual-clutch gearboxes

Genuine G 052 529 oil for S tronic dual-clutch gearboxes. One litre, if you need to top it up.

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Read more

• Gearbox repairs
• Gearbox servicing
• Audi A4 B8 3.0 TDI service schedule
• Gearbox service intervals for VAG cars
• DSG DQ250: when does the mechatronic unit fail and what should you do?
• DSG DQ381 and DQ500 with wet clutches: when should you change the oil?
• Multitronic: why does it judder and can it be repaired?

Frequently asked questions

How many separate oils does the S tronic 0B5 use?

Two. One is for the clutches and mechatronic unit, while the other lubricates the gears and differential. They're different oils and need changing separately.

How often should I change the oils in my S tronic?

Every 60,000 km, using genuine oils and filters. And I mean both oils, not just one.

How can I tell whether it's the mechatronic unit or the clutches?

By checking live diagnostic data. We look at the pressure, clutch slip and adaptation values. That way, we find the real problem instead of replacing parts blindly.