Hoovey689

iTrader: (16)

Report: Xtrac develops cheaper gearbox that behaves like dual-clutch

Dual-clutch transmissions are the current Holy Grail when it comes to transferring underhood power to the wheels of the car. Nearly every automaker that does serious business around the world offers DCTs, and the ones that don't very likely soon will.

It's easy to understand the draw of the DCT: better performance and greater efficiency. But there are also problems. For instance, two clutch mechanisms mean (theoretically, of course) twice the potential repair costs, and DCTs are generally more expensive than either standard manual transmissions or conventional automatics with torque converters.

Xtrac, a company firmly entrenched in transmissions for racing applications, has developed a new technology called the Instantaneous Gearchange System, which uses a ratcheting mechanism to couple the gear hubs with the main shaft. The system has been under development for two years and has reportedly been put into race duty by multiple motorsports teams.

Apparently, the IGS technology will be less costly than other dual-clutch transmissions and could potentially be adopted by various global automakers.

http://www.autoblog.com/2010/12/04/r...-like-dual-cl/

mmarshall

I'm a believer in the DCT concept myself, and have always liked the way that VW/Audi do the DCT mechanism with the DSG/S-Tronic gearbox (too bad Audi seems to be phasing out most of the S-Tronics for conventional Tiptronics in their U.S.-market versions). This is a superb gearbox, and I hate to see it go. I've tried a few other DCTs, such as the one in the Ford Fiesta, but nobody, IMO, seeme to be able to do it like VW/Audi.

Whether the IGS will meet or exceed the driveability, performance, and capabilities of the DCTs remains to be seen...........I won't comment further on that until I've actually sampled one.

That, of course, remains to be seen. To get good durability in transmission parts, one must use quality materials (among other things, of course). In general, the more durable/higher-quality the part, the more expensive it will cost (or can cost). An example is case (carbon-hardened)-steel. It may cost more than regular steel, but there is a reason. And getting good durability out of lighter-weight aluminum can be even more costly. That's one reason why today's transmissions are relatively expensive....the attempt to combine durabilty with light weight.

As far as the current "Holy Gail" or efficiency is concerned, most transmission engineers would probably say that the CVT, with its unlimited-gear range, probably offers the greatest potential fuel mileage. But CVT's have several drawbacks.....they sometimes tend to have surging, "rubber-banding" or "motorboating" characteristics, drive-belt durability/longetivity problems, and are generally better-suited to lower-torque engines rather than higher-torque ones. Nissan and Subaru, IMO, current offer the best-driving CVTs, with the least driveability problems, but even they are not foolproof, and have had some durability recalls.

Big Andy

The Lexus CVTs seem to be smooth and reliable. I've also never heard of one giving problems.

mmarshall

You might have a point. But the only Lexus CVT I've sampled lately was in the HS250, and that is a fairly new vehicle, with most of the HS transmissions probably not (yet) having a lot of mileage and wear on them for a real durability test.

chikoo

Before I became an engineer, I always thought automatic transmissions were actually the stick shifts which were shifted by the car itself!!! LOL.
It is now becoming a reality.

chikoo

Mike, I thought case hardened steel was the norm? Is it not?

In my prior life, I was involved with manufacturing heavy machinery and we case hardened all the gears.

mmarshall

Yes, by that statement, I was not suggesting that today's transmissions are necessarily made out of cardboard. I was merely using the carbon-case-hardened steel vs ordinary-steel comparison as an example of using better-quality parts at a (sometimes) more-expensive cost. A lot of today's transmissions, though, have aluminum cases to save weight. And, though I may not necessarily still apply to today's units, I can remember vividly the the atrocious quality of the transmissions used on many American-nameplate vehicles from the late 70's through the 1990s, especially the first front-drivers. Some of them, like when GM, in a bid to cut costs, deliberately used smaller, lighter automatics designed for 6-cylinders on V8-equipped vehicles in the late-70s, led to class-action suite from buyers caught in the huge transmission-failure-rate. The infamous Chrysler 4-speed Ultradrive of the 1990's was another example.

Don't want to get too far-off-topic, though....the new XTrac unit.