Reliability of SMG?

I asked this same question to Roundel Tech Talk columnist Mike Miller a few months ago. Here's his reply...

I've driven SMG-equipped BMWs extensively, and while the system works differently on different models, my personal opinion has never changed -- I very much prefer a traditional manual gearbox. For me, clutching is fun and I prefer the confidence that comes only with positive manual control over vehicle systems in general. I'm also proud of my ability to handle the clutch and the shifter. I can shift just as well if not better than the computer. Moreover, the SMG clutch is controlled by a dizzying network of electronics and electro-hydraulics. I would not want to be the one holding the check book when the system malfunctions out of warranty. Besides, I prefer to keep my cars simple. That said, SMG works -- it does what it is supposed to do and it does it well, in my opinion.

At the same time, I will readily admit to being a hardcore, grease-under-the-nails, traditional Bimmerhead. It's not my daily driver, but I still own a 2002.

SMG-equipped BMWs have not aged long enough for me to formulate a hard opinion on durability and reliability, but, given that dizzying network of electronics and electro-hydraulics, I think it's safe to say SMG's clutch will have more problems than a traditional clutch -- which usually has no problems at all. As for the gearbox itself, it's pretty much a standard BMW manual gearbox with the SMG clutch and some servo motors. The biggest problem we see with BMW manual gearboxes today is that they basically wear out now that no one changes the oil in them; same with differentials. The failures generally occur over 100,000 miles, and I wouldn't expect the SMG to be any different.

Of course, if you change gearbox and differential oil at reasonable intervals and use good synthetic lubricants, chances are good the components will last indefinitely. I use Red Line Oil

and have for over 20 years. The cars I service never need new gearboxes or differentials.

The biggest problem I see presently with SMG BMWs is not really a problem with the system but with the buyers, who think they are getting an automatic transmission; they are not. It's a manual gearbox with an automatic clutch, and that's exactly the way it shifts -- not like an automatic. As for the future, I think we'll see SMG evolve. After all, changing the way it shifts is as simple as a few more lines of computer code. In fact, I think we'll see SMG replace the traditional manual gearbox altogether, and within less than ten years. SMG is very popular among the doo-dad crazy Europeans, and BMW can't quite understand why some of us Americans don't "get it" and still want the clutch pedal. Of course, they also don't understand driving a car with 250,000 miles. In the end, they'll take away our clutch pedal just like they took away our limited slip differentials and like they gave us i-Drive -- whether we like it or not. SMG and automatic transmissions allow BMW to exert a great deal more control over the way the car is driven. Areas such as time in gear, rpm limitations, clutch slip in the SMG, and gear selection itself all affect emissions and fuel economy. The traditional manual gearbox simply allows too much control at the hands of that last vestige of imperfection -- the driver.

Anyway, this is why I'm buying a 2005 325Ci 6-speed manual. I hope I'm wrong, and I'll always remain loyal to the Blue and White, but I can foresee the 325Ci being my first and last new BMW car.

Best regards, Mike Miller

Nice post Kyle, very useful info. I agree totally with Mike Millers comments as to complexity vs simplicity. I'll take simplicity any time! And, driver involvement is the only thing worth while, let's keep it as long as we can ;-0

Chris

"Mike Miller" was quoted in news:bVUBf.15753$ snipped-for-privacy@tornado.tampabay.rr.com:

What would be considered "reasonable intervals"?

Kevin

Any time BEFORE it starts to miss shifts. :-}

I suspect these should be changed at the Inspection II interval, whatever that is (~30k miles?).

Randy

Well, the *old* maintenance schedules (i.e., pre- 2000) recommended that transmission and differential fluid be changed every 30,000 miles. Of course, there are many here who don't believe in that and consider it a waste. Nevertheless, if you decide to follow this, then a good synthetic like Redline or Royal Purple works well.

Don't forget that the *old* maintenance schedules also recommended flushing brake fluid and coolant every 2 years too.

I'd tie it to the service interval lights: Insp 1/2. These come pretty close to the 30K intervals of old, certainly close enough to do no damage.

R / John