OTHING HAS SCARED OFF WOULD-BE MECHANICS over the years like the automatic transmission. These modern marvels harness an engine’s brute horsepower and convert it into usable energy to drive the vehicle. From basic and unreliable beginnings, today’s transmissions boast greater efficiency and reliability while demanding more from the fluids that lubricate, cool and protect these complex machines.

What is a Transmission?
Transmissions convert engine power into vehicular movement. But they do far more. A transmission is not merely a mechanical device, but almost a "thinking" machine. An engine runs best within a specifi c RPM range, achieving optimum fuel economy and lower engine stress. The transmission must not only deliver power to the vehicle’s wheels, but do it while keeping the engine running at the optimum RPM. Rather than engine power simply flowing to the wheels, the transmission fi rst pulls it through finely tuned gearsets and measures factors such as engine RPM level, driving direction and speed, and then sends the newly harnessed power through the drivetrain, turning the wheels.

How do Transmissions Work?
Easily the most complicated mechanical system of almost any vehicle, an automatic transmission features an array of individual parts designed to work together. Some of the more basic parts include the following:

• Planetary Gearsets
• Torque Converter
• Valve Body
• Oil Pump
• Clutch Packs
• Computer Controls

Planetary gearsets are the key to how the transmission works. The number of planetary gearsets within the transmission varies depending on how many speeds it offers. Three components make up a single planetary gearset: the ring gear, the planet gears and the sun gear. As the name suggests, the sun gear centers the gearset, with the planet gears "revolving" around it. The ring gear wraps itself completely around the sun and planet gears, holding the entire system together. The ring gear also transfers the power from the engine into the planet gears, driving them, and in turn driving the sun gear.

Things now get complicated. The sun gear is not directly connected to the transmission’s output shaft (if it were, the vehicle could not sit idle without moving). Instead, a clutch pack forms a controllable bond between the planetary gearset and the output shaft. Highly pressurized transmission fluid activates the clutch pack, squeezing the clutch plates inside the pack together and enabling the shifting process. To enable engine idling, the clutch activates, or "tells," the clutch pack to release the sun gear, breaking the controllable bond between it and the output shaft. Now the engine can turn the sun gear without propelling the vehicle.

Today’s six-, seven- and even eight-speed automatic transmissions feature a mind-boggling range of gearsets combined in various ways. Tracing the flow of engine power through this maze of moving parts and pressurized transmission fluid can baffl e even the most seasoned mechanics.

The Role of Transmission Fluid
Transmission fluid does far more than simply lubricate; it also must cool the transmission and withstand the pressure needed to manipulate the internal parts that control shifting. Every aspect of the transmission functions on a steady supply of pressurized fluid. Just a few minutes of operation without this vital fl uid supply can ruin a costly transmission. With this is mind, AMSOIL offers two different synthetic automatic transmission fluids for passenger vehicle applications, both of which provide outstanding performance and protection in severe operating conditions.

AMSOIL Synthetic Universal Automatic Transmission Fluid (ATF)
AMSOIL Synthetic Universal Automatic Transmission Fluid is engineered to outperform conventional automatic transmission fl uids and exceed the performance requirements of most North American, European and Asian vehicles. AMSOIL ATF protects against sludge and varnish deposits, and resists oxidization two times longer than required for petroleum ATFs. AMSOIL Synthetic Universal ATF is recommended for a broad range of transmissions, hydraulics, power steering and other applications and is the recommended fluid for applications specifying DEXRON®III, MERCON® and MERCON V and Chrysler ATF+4®.

AMSOIL Synthetic Fuel Efficient Automatic Transmission Fluid (ATL)
AMSOIL Synthetic Fuel Efficient Automatic Transmission Fluid is a low-viscosity, lightbodied fl uid engineered to exceed the requirements of GM, Ford and Toyota where low-viscosity oil is required. However, this special, lighter formulation still boasts outstanding performance and protection.