Automatic Transmission Systems Flashcards

In a simple planetary gearset, the ring gear is held and the sun gear is the input. What is the result at the carrier?

Answer: Maximum forward gear reduction

With the ring held, driving the sun makes the carrier turn slowly in the same direction, which gives maximum reduction.

When any two members of a simple planetary gearset are locked together, what ratio results?

Answer: Direct drive (1:1)

Locking two members makes the whole gearset turn as a unit at a 1:1 ratio.

Which planetary combination produces reverse?

Answer: Carrier held, sun input, ring output

Holding the carrier makes the pinions act as idlers, so the ring turns opposite to the sun.

Transmission fluid is dark brown and smells burnt. What does this usually indicate?

Answer: Overheated or burned friction material

A burnt odor and dark color point to overheating and worn clutches or bands.

On most dipstick-equipped automatics, how should fluid level be checked?

Answer: Engine running, at operating temperature, in Park on level ground

Fluid expands when hot and fills the converter and passages with the engine running, so these conditions give an accurate reading.

Why is there usually no engine braking when coasting in first gear with the selector in Drive?

Answer: The one-way clutch overruns during coast

A one-way clutch holds only in the drive direction, so it freewheels when the wheels drive the engine.

Which fluid should be used to service a belt- or chain-type CVT?

Answer: Only the CVT fluid specified by the manufacturer

CVTs need fluid with specific friction properties for the belt and pulleys, and the wrong fluid can cause slipping and damage.