What is it about transmissions that fascinates me? Maybe that is too strong a word, but the interest is really there. I just remember the times that the only choice was "automatic or manual" and remember reading about the times that manual was the only choice. Today we have automatics and manuals, of course, but also computer-controlled manuals, CVTs and now dual-clutch... ummm... what are they? Automatics? No, they really are a new category.

First we have some really good news for BMW enthusiasts. BMW will finally replace their SMG transmission, a computer-controlled manual, with a dual-clutch unit. The old SMG was a seven-speed unit and the new M DCT will be a seven-speeder too. The six-speed manual will be still available, but will be slower in acceleration, some 0.2 seconds to 60 miles/hour with the gap growing larger at higher speeds. It will be available in Europe in March 2008 in the M3.

The new "M DCT" (don't we just love strange letter combinations?) will be made by BMW's manual transmission vendor, Getrag. It should be vastly better than the SMG transmission in terms of smoother shifting and operation in the automatic mode. I would expect that it will replace the SMG in the M5 and M6 shortly after its introduction.

The transmission will be controlled by a combination of shift lever, probably something like the new joystick in the X5, and steering wheel paddles. BMW claims that the transmission has been developed exclusively for them and will be used in 3-series and 5-series cars.

What's new for automatics? The most significant new transmission, or at least updated, is the second generation six-speed 6HP, the 6HP28, which replaces the 6HP26 introduced in 2001. It has been upgraded so that it now takes on the "DNA" of the car that it is installed in. This means that when it is in a Jaguar it will feel different than if it is in a BMW.

The redesigned transmission will shift some 50% faster. Also there will be about a 3% increase in fuel economy with gasoline engines, 6% with diesel engines, because of a new torsional damper design. The new torque converter improves the connection between the driveline and the engine, allowing the driver to feel a more active and direct response when accelerating. The objective is to close the clutch completely as soon as possible, again increasing fuel economy.

Downshifts are performed in up to four stages without any time losses or noticeable deceleration. To find a target gear, control electronics determine the optimum gear based on load conditions, driving situation, and vehicle speed. For example, if the driver is cruising in sixth gear and wants to accelerate rapidly, the transmission needs just 100 milliseconds to trigger the change from sixth to second gear. The response time for downshifts is approximately 200 milliseconds (that's 0.2 seconds), which ZF claims to be below the limit of the driver's perception.

The new transmission uses a Lepelletier gear set. I like that name, which is patented by ZF. Whatever it is, it allows the six transmission ratios to be made with fewer components than the previous five-speed transmission. Therefore it weighs less. A plastic oil pan also reduces weight.

Since engines are producing more power these days, more significantly to the transmission, more torque as well. The new transmission allows for that too with a capacity of 520 lb-ft of torque. It weighs 210 pounds. It's made in Germany and is now seen in the BMW 3-series coupe, X3, and X5. With that torque capacity, it can also be put in the V-12 BMWs.

ZF made over 1 million six-speed automatics in 2006.

What's on the horizon for automatics? More speeds, of course! With Mercedes manufacturing their own seven-speed transmissions for a couple of years, and Toyota now equipping their LS with an eight-speeder, how could ZF resist? ZF announced their answer, the 8HP, which will be available on 2010 model-year cars. It will have a torque capacity the same as the outgoing 6HP and be in about the same size package. Note that the Aisin (Toyota) eight-speed transmission has a torque capacity of just 405 lb-ft for comparison to ZF's 520.

ZF engineering claims that compared to a three-speed automatic, a four-speed unit would allow about 6% better fuel economy. Going from four-speeds to five gains about 2% more. Their first generation six-speed unit brought about an increase of 5% more yet. Note, we're up to 13% so far. As I said before the new generation six-speed unit gets another 3% to 6%. The 2010 eight-speed transmission will bring another 5% in fuel economy. That is really a sizeable increase over those ancient three-speed transmissions.

A large part of this fuel economy increase is because more gears allows the spread of ratios to be bigger. The new 8HP has a ratio spread of 7.05 compared to the 6HP's spread of 6.04. Aisin's six-speed has a spread of 6.7. The maximum step size between gears on the 8HP is 1.5 versus 1.8 on the 6HP.

Aisin points out that fuel economy isn't the only benefit of more transmission speeds. Vehicle performance also can be improved. Their eight-speeder allows the engine to stay in its "sweet spot" more often during driving.

The upcoming ZF is a modular design so that various elements can be redesigned without changing the whole package. Right now, they're experimenting with eliminating the torque converter by using a special "starting clutch".

Oh yes, the transmission also is designed to allow all-wheel drive or hybrid drive variations -- both starter/alternator types as well as full-parallel systems.

The new transmission will be shown publicly at the upcoming Frankfurt Auto Show in September.

Right now, the "standard of the world" transmission is the AA80E from Aisin found in the Lexus LS. They claim to be the most buttery-smooth and quiet production transmission. Mercedes disputes this by claiming that independent tests by "meer mortals" comparing the Aisin to their own W7A700 found in most Mercedes cars is indistinguishable.

But if eight is so great, wouldn't nine be finer? Let me quote Hamid Vahbzadeh (don't ask me to pronounce his name) who is Director of Advanced Power Transfer and Global Transmission Innovation Manager for GM (what a title!): "Looking at the execution of these new seven- and eight-speed transmissions, you realize that the added benefit of going to a higher number of gears and perhaps a slightly higher ratio spread -- the incremental fuel economy benefit, for example -- pretty much washes out with the added parasitic losses inside the transmission. And those that have a second-gear stop for normal driving, for all practical purposes function as a six-speed." And which transmissions, exactly, is he referring to?

He continues to say that there are advantages of going from four to five to six speeds, but the advantage is much smaller, if any, above that. Of course, he is speaking from the perspective of a mass-market manufacturer -- GM -- not a premium market manufacturer that ZF delivers their transmissions to -- BMW, Jaguar, Lexus, etc. --who can afford the extra cost for the bragging rights. The problem for GM is that they want Cadillac to compete in that market, so they will inevitably either have to develop an eight-speed transmission or buy one from an OEM.

He hedges his bet with the statement, however: "If one would get really smart and execute, let's say an eight-, nine-, or even a ten-speed in such a dramatic configuration that would allow a much wider ratio spread, but at lower parasitic losses, then yes, you will have added some fuel economy and performance benefits." What's the limit? "It's a good question that really depends on the technology. I cannot rule out that someday we might have a 15-gear-ratio transmission. I'm sure many companies are working on concepts intended to allow an increased number of gears without significantly adding to the internal losses."

Note that if -- and this is a really big "if" -- engineers can design the control logic for a dual-clutch transmission to be as good as a current automatic, meaning smooth, that transmission would replace a traditional automatic. That's the dual-clutch is much simpler mechanically than a traditional automatic. And that means that more gears would be easier to achieve.

Welcome to transmission wars!