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 (www.redlineoil.com) 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.
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
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.
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