Originally Posted by vsssarma
You have Dual Clutch Transmissions, Continuously Variable Transmissions, Automatic Transmissions and Manual Transmissions.
- Dual clutch transmissions (DCTs) are the fastest growing passenger car segment in the world, with a forecasted growth of 200% by 2017, especially in Europe, North America and China. There are two types of DCTs: wet and dry clutch. Unlike the dry variant, wet clutch DCTs are immersed in a lubricant. A wet DCT fluid must provide wear and synchronizer friction performance similar to a manual transmission fluid, as well as frictional properties similar to an automatic transmission fluid. Because of these unique requirements, neither a traditional MTF or ATF will suffice; a dedicated wet DCT fluid is needed.
- Continuously variable transmissions (CVTs) offer enhanced fuel efficiency over traditional automatic transmissions, making them increasingly popular choices for both passenger cars and in off-highway applications in Japan, China and the U.S. There are two main types of CVTs, belt or chain type, with similar lubrication needs. Since they both generate high metal-to-metal friction performance, they require unique metal friction performance, making them very different from a traditional stepped automatic transmission.
- Automatic transmission fluid (ATF) is the most complex of all lubricating fluids. Not only does it have to reduce friction to prevent wear like all lubricants, but it also has to allow a certain level of friction so clutch materials can engage. Since most OEMs use proprietary frictional materials, virtually every ATF is OEM-specific. In some cases, they're transmission-specific. To improve fuel economy, transmission components are lighter, despite increased engine horsepower. And new fuel-efficient transmissions exhibit higher torque and higher operating temperatures. All these factors are stressing the ATF severely. Problems such as transmission shudder, poor shift feel and accelerated wear are becoming more common as drain intervals are increased.
- There are two main types of manual transmissions (MTs): synchronized and non-synchronized. Non-synchronized transmissions are more common in North America heavy duty vehicle applications. The focus on driver comfort has improved the designs of today's transmissions, especially in terms of shift feel and durability. The drive for improved fuel economy has also led to advancements in design and the use of a wide range of synchronizer materials. These changes in transmission design have led to advancements in transmission lubricant additive technology highlighting the importance of using a dedicated manual transmission fluid (MTF) that is matched to the frictional properties of these more complex materials.
Please stick to manufacturer's recommendation of specification to be used.
There is one more type that can be added to the CVTs. The Toyota Hybrids uses a CVT that uses a planetary gearset. No belt or chain. Because of that, they only spec there WS ATF for that transmission.
