Automatic Transmission Questions and Answers

Answer: A

A torque converter is a fluid coupling that allows the engine to idle while the vehicle is stationary and transmits torque through oil rather than friction. The planetary sets provide the ratios. The converter also multiplies torque, which a clutch cannot do. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Most errors here come from carrying across a result from a neighbouring case where it does not hold.

Answer: B

The impeller is driven by the engine, the turbine drives the gearbox, and the stator redirects the returning oil to multiply the torque. A lock-up clutch is an addition rather than one of the three elements. The stator is what distinguishes a converter from a simple coupling. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Naming what changes and what stays the same is the reliable route through questions of this shape.

Answer: C

The stator redirects oil leaving the turbine so that it rejoins the impeller helpfully rather than opposing it, and the reaction torque is added to the output. Without a stator the device is a fluid coupling with no multiplication at all. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Most errors here come from carrying a result across from a neighbouring case where it does not hold.

Answer: D

The stator must be held against the reaction torque at low speed but must freewheel once the turbine approaches impeller speed. A rigid mounting would cause it to obstruct the flow and destroy the efficiency at cruise. The one way clutch handles both conditions. Naming what changes and what stays the same is the reliable route through questions of this shape. A symptom that appears under one condition and not another is what narrows the diagnosis quickly.

Answer: A

As the turbine speeds up, the oil striking the stator changes direction and the stator freewheels, after which the converter acts as a plain fluid coupling. Some slip always remains without lock-up, so the turbine never quite matches the impeller. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. The order in which the effects act is what decides the outcome, so it is worth establishing first. Checking the units of each quantity catches a wrong formula before the arithmetic begins.

Answer: B

Stall occurs with the brakes on and the throttle open, and it is the condition of maximum torque multiplication, typically around two to one. Stall speed is the engine speed reached in that condition. A stall test reveals converter and transmission faults. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Tracing the requirement back to the physical constraint that produces it makes the answer follow.

Answer: C

A stator that freewheels when it should be held cannot multiply torque, so the engine reaches a lower speed than specified. A restricted exhaust or a weak engine gives the same reading, which makes the last option a genuine alternative to rule out. The order in which the effects act is what decides the outcome, so it is worth establishing first. The shared behaviour explains why these belong together and the differences explain why both exist. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: D

If a clutch pack slips, the engine accelerates beyond the specified figure before the transmission absorbs the torque. A seized stator produces poor high speed performance and overheating rather than a high stall. The two symptoms are distinct. Checking which component actually carries the load settles most questions of this kind at once. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: A

Even at cruise a converter slips a few per cent, wasting fuel as heat, so a friction clutch locks the turbine to the cover. Multiplication is lost, which is why it engages only at steady speed. It typically saves several per cent of fuel. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: B

Lock-up is applied only when the engine is not being asked to accelerate hard, because the converter's damping is lost when it engages. Fluid temperature is genuinely used as a condition on many systems, which makes the last option a real consideration. The shared behaviour explains why these belong together and the differences explain why both exist. Most errors here come from carrying across a result from a neighbouring case where it does not hold.