BMW M Double Clutch Transmission Explained
Posted by Anthony Carbone 2 Sep, 2008

The new BMW M Double Clutch Transmission gearbox is said to be the first dual-clutch automated manual developed for sporty M-type production engine speeds of up to 9000 rpm! When compared to a conventional automatic, the new gearbox allows for greater fuel economy due to a more direct connection with the engine, as well as the larger number of gears (7 vs. 6) which yield a greater overall gear-ratio spread of 4.8.
The “Double-clutch transmission†is BMW’s technical name for their automated-manual transmission. Yes this sounds somewhat contradicting but bear with the name for a moment.
It is constructed like a manual transmission BUT can shift automatically and has NO clutch pedal. WHERE IS THE FUN IN THIS YOU ASK?? I am not sure, but I have a sneaky suspicion that driving one might change both of our minds as quickly as it would take us to bang through the first 3 shifts!
The advantage to its Manual/Automatic engineering is that you get an automatic that shifts extremely quickly compared to a traditional automatic and also takes up less space and also weighs less.
The BMW M Series of performance engineering cars will all be equipped with this new transmission system.
Now, there’s is also a single-clutch automated manual that’s found in less performance oriented cars like the Smart ForTwo which are fuel economy engineered. A single-clutch system may not be as smooth as a dual-clutch because the clutch has to disengage, choose a gear then re-engage. With a dual-clutch system the next gear can be staged and ready to shift before you’re even out of the previous gear, so slamming through gears at high rpm’s is flawless and sharper than anything you have previously driven (unless your driving an F1 car).
Click Image for Detailed Explanation of Components

You may also hear a double-clutch transmission called dual-clutch, clutchless manual, twin-clutch, etc. As previously mentioned, you get quick shifts, but for drivers it means there’s no clutch pedal and shifting can be controlled through either paddle shifters on the steering wheel or via a plus/minus gate on the shifter.
You don’t, however, have to use the paddles or plus/minus gate; most cars with these transmissions also have an automatic mode, where the transmission will shift on its own like a regular automatic. Shifting on its own is where you’ll find the downside to these transmissions, as sometimes that shifting can be jerky or feel unnatural in day-to-day driving.
I’m sure this double clutch transmission system is super amazing, but it’s definitely hard to wrap your head around driving a fun sporty performance oriented sports car without a CLUTCH and essentially shifting by wire.
Some purists who would never be caught dead driving an “F1 Style Paddle-Shift Transmission” have been known to rave about the new F1 Transmission in the Ferrari F430. I know first hand my business partner Vinay has changed his tune after logging many hours and km’s in one of his best friends new Ferrari F430 Coupe that has the F1 style transmission.
Checkout the Video below to SEE and HEAR how effortlessly and quickly one can shift with these F1 inspired engineered gearboxes.
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[Source: SAE.org, Ask.Cars.Com]
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Good Article, Anthony. Audi has had their double-clutch tranny for a few years, and now that Nissan has theirs (GT-R) and Porsche’s PDK is just around the corner, it is about time BMW switches their SMG trannys to double-clutch mechanisms.
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