Automatic Transmission Fundamentals

What are the three major functional sections that make up all automatic transmissions, whether longitudinal RWD or transverse FWD transaxle units?

Bell housing, oil pan, and extension housing. Oil pump, Governor, and Drive Link assembly. Torque converter, planetary gear set unit, and hydraulic control system. Fluid coupling, stator support, and non-computer electrical control.

What is the main objective in the development of the automatic transmission?

To increase the maximum available engine torque by 3.00:1. To provide a permanent 1:1 ratio once the coupling point is reached. To relieve the driver of the physical effort and coordination needed to operate a clutch pedal and a standard transmission shift lever. To allow the engine to be started without relying on a flex plate.

In an automatic transmission operating in overdrive, how does the output speed and input torque compare to the input speed and output torque?

Output speed is less than input speed, and input torque is less than output torque. Output speed is equal to input speed, and torque is unchanged. Output speed is greater than input speed, and input torque is greater than output torque. Output speed is greater than input speed, and input torque is less than output torque.

What must happen when the transmission reaches the coupling point during acceleration?

The impeller rotation must stop instantly. Torque multiplication increases rapidly to 3.00:1. The stator one-way clutch must freewheel. Vortex flow must be at its maximum.

What is the approximate maximum ratio of torque multiplication provided by a three-member torque converter during a stall condition?

0.50:1 1.00:1 2.00:1 to 3.00:1 4.00:1

For practical purposes, when is the coupling point assumed to be reached in a conventional torque converter?

When the impeller speed matches the turbine speed exactly. When the vehicle reaches 65 to 95 km/h (40 to 60 mph). When the turbine reaches 9/10 the speed of the impeller. When the torque multiplication ratio is 2.00:1.

What condition occurs when the oil flow within the torque converter is termed vortex flow?

The impeller and turbine are turning at approximately the same speed. Low heat, high output speed, and low torque are created. The turbine is turning at a lower rate of speed than the impeller. The stator is freewheeling, allowing it to rotate clockwise.

Vortex flow is greatest when the turbine is stopped and the impeller is turning as fast as the engine can, a condition known as:

Rotary flow. Coupling speed. Stall condition. Freewheeling.

When does rotary flow (coupling point) in a torque converter create the greatest torque output?

Rotary flow creates maximum torque output. Rotary flow is greatest when the turbine is stalled. Rotary flow is not related to torque output; it is a mechanical lockup. Rotary flow is greatest when torque output is the lowest.

What is the explicit purpose of the stator in a non-lockup torque converter?

To absorb shock loads and vibration. To provide a mechanical link to the transmission gear train. To intercept the oil coming out of the turbine and redirect it back to the impeller to assist rotation. To provide a neutral condition at low engine RPM.

The redirection of oil flow by the stator increases engine torque by an approximate 2.00:1 to 3.00:1 ratio. The exact amount of torque multiplication depends on what physical characteristic of the converter?

The material of the transmission case. The thickness of the impeller drive lugs. The angle of the vanes in the elements. The compression of the torque converter clutch spring.

The stator in an automatic transmission uses a one-way clutch (overrunning clutch). What is the purpose of this clutch?

To force the stator to turn counter-clockwise against impeller rotation. To lock the stator to the stator support during vortex flow. To provide a frictional drag when the impeller is turning faster than the turbine. To lock the turbine to the impeller at coupling speed.

What happens to the sprag clutch in a one-way clutch assembly when the impeller and turbine are operating at the same speed (freewheeling/overrunning)?

The sprags pivot toward their long diagonals, locking the races. The outer race rotation forces the sprags to lock the races. The sprags pivot toward their short diagonals, releasing the clutch. The sprags are forced to rotate at the same speed and in the same direction.

What component does the torque converter turbine element (output element) transfer power to?

The engine flywheel (flex plate). The stator support. The transmission input shaft. The transmission oil pump drive gear.

What is the required condition of the stator during vehicle acceleration (before coupling speed) to achieve torque multiplication?

Freewheeling (overrunning). Rotating clockwise. Held stationary (prevented from turning). Turning counter-clockwise.

What is the fundamental difference between a fixed displacement pump and a variable displacement pump in an automatic transmission?

Fixed displacement pumps use helical gears, while variable displacement pumps use rotor types. Fixed displacement pumps draw fluid from the transmission sump, while variable displacement pumps use an external reservoir. Fixed displacement pumps (gear/rotor types) discharge a constant amount of oil proportional to engine speed, while variable displacement pumps (vane type) vary output according to transmission needs. Fixed displacement pumps require high pressure regulation, while variable displacement pumps do not.

Gear-type pumps are often referred to as crescent pumps for what reason?

They use gears that mesh at a 90 ∘ angle. They are driven by the externally toothed gear. Due to the crescent-shaped part of the body that protrudes into the area where the gears are not in mesh. They are made of stamped steel, similar to the oil pan.

What is the function of the large area of the inlet port compared to the outlet port in a fixed displacement pump?

It ensures that the fluid flow creates pressure. It prevents the rotor tips from flowing between the inlet and outlet chambers. It allows unrestricted oil to flow into the inlet (suction) port of the pump. It reduces the discharge flow proportional to engine speed.

Automatic transmission pumps are classified as positive displacement hydraulic pumps. What does this mean concerning their operation?

They can develop fluid flow only when the transmission is in a forward gear. The pump inlet and pump outlet ports are sealed from one another. They can only deliver oil when the pump is turning at engine speed. They deliver more fluid than the transmission needs, resulting in excess volume.

Which component controls the output volume and system pressure of a variable displacement vane pump?

The priming spring. The slide guide ring. The pressure regulator valve. The torque converter hub drive gear.

What action occurs to reduce the output volume of a variable displacement vane pump when system pressure increases?

The pressure regulator valve closes, allowing the priming spring to expand. The rotor speed is reduced by the transmission input shaft. Oil is directed to the slide fluid pressure chamber, forcing the slide against the priming spring to reduce the inlet chamber size. The vane guide ring is locked to the rotor assembly.

What is the required condition for a hydraulic system to develop pressure?

The pump must be variable displacement. Its flow must be restricted or closed. The fluid must be forced into the inlet side by atmospheric pressure. The pump must discharge an amount of oil proportional to engine speed.

The transmission oil pump must constantly circulate a small volume of oil through the converter, oil cooler, and transmission to prevent overheating. What is the ideal running temperature range for the transmission?

Below 55 ∘C (130 ∘F). 37 ∘C to 80 ∘C (100 ∘F to 175 ∘F). Above 150 ∘C (300 ∘F). Below 20 ∘C to prevent oxidation.

Why do manufacturers build an oil cooler into the radiator, and sometimes offer an auxiliary cooler mounted in front of the radiator?

To prevent the oil from foaming due to excessive heat. To ensure the torque converter is kept full of oil under low pressure. Because heavy loading or trailer hauling can cause converter temperatures to rise considerably above the ideal range. To maintain fluid pressure between 30 and 70 psi.

The size of an aftermarket transmission cooler is determined by the combined Gross Vehicle Weight (GVW) of which components?

The transmission, torque converter, and engine. The front and rear drive axles. Both the tow vehicle and the trailer being towed. The transmission and the planetary gear set.

Why is a red dye added to most automatic transmission fluids?

To ensure non-corrosion to metal parts. To reduce foaming when agitated. To distinguish it from engine oil. To enhance oxidation stability.

ATF Type F is characterized by having which specific property that transmissions requiring it require?

Excellent fluidity at low temperatures. A high-frictional coefficient. A low pour point to ensure quiet operation. Seal swell agents for compatibility with modern high-temperature seals.

Automatic transmission fluid (ATF) consists of approximately what percentage of base oil and performance additives?

70% base oil and 30% additives. 85 to 90% base oil and 10 to 15% performance additives. 50% base oil and 50% additives. 95% base oil and 5% additives.

What is the purpose of the Torque Converter Clutch (TCC) in lockup converters?

To multiply torque from the engine at stall speed. To absorb and dampen engine power pulses. To provide direct drive from the engine to the transmission. To provide a no-drive condition at low engine rpm.

Which major advantage is provided by the lockup torque converter over the conventional non-lockup type?

Increased torque multiplication up to 4.00:1. Elimination of slippage (which reduces operational heat and improves fuel economy). Elimination of the need for planetary gear sets. Reduction of hydraulic control system complexity.

A lockup converter is known as a four-member (element) converter because it contains the standard three elements plus which additional assembly?

A centrifugal weight system. A converter clutch assembly. A permanent stator lock. A split guide ring.

The apply piston/plate in a lockup converter incorporates what component to reduce torsional vibration when the converter is locked?

Belleville springs. Centrifugal weights. Torsion springs. Pinion position shims.

How is the process of locking the lockup converter clutch accomplished?

By shutting off fluid flow completely to the transmission input shaft. By reversing the oil flow, forcing fluid into the back side of the converter. By utilizing the centrifugal force of the impeller to apply the clutch. By engaging the brake switch, which prevents clutch application.

What is the state of fluid flow through a lockup torque converter when the lockup clutch is in its engaged position?

Maximum vortex flow. Rotary flow with maximum slippage. Fluid flow stops, and pressure builds to a predetermined value. Fluid flows outward, pushing the apply piston back.

The lockup clutch in a non-computer controlled vehicle will only engage when the transmission is in which specific gear?

Fourth (Overdrive) gear. Third gear. First gear (Reduction). Reverse gear.

In a non-computer controlled vehicle, which condition is one of the ways the locked converter can be unlocked?

Accelerating the engine to increase engine vacuum above 3" Hg. Slowing down to below 65 to 40 km/h (40 to 26 mph). The engine coolant temperature drops below 55 ∘C (130 ∘F). Manually shifting into the 4th gear overdrive position.

Which sensor is monitored by the PCM to prevent the torque converter clutch from applying until the engine reaches its operating temperature?

Vehicle Speed Sensor (VSS). Throttle Position Sensor (TPS). Coolant Temperature Sensor (ECT). Transmission Oil Temperature Sensor (TOT).

In the event the Transmission Oil Temperature (TOT) sensor detects an overheat condition, how may the PCM modify the TCC operation?

By delaying shift points to reduce gear speed. By increasing the voltage to the brake switch. The torque converter may be locked earlier to eliminate heat build-up. The motor lock circuit is de-energized, applying the lock.

What is the explicit function of the Brake Release Switch signal when received by the PCM?

To engage the torque converter lockup clutch immediately. To provide the necessary pressure for the TCC switching valve. To prevent the torque converter clutch from applying. To allow manual downshifting from third gear.

Automatic transmission fluid is defined as a fluid rather than an oil primarily to differentiate it from which other type of lubricant?

Gear oil (GL-5). Engine oil. Hydraulic brake fluid. Power steering fluid.

Automatic transmission fluids (ATFs) must maintain a high viscosity index to ensure what performance feature is retained?

Corrosion control. Seal compatibility. Adequate lubricating film thickness for severe high-temperature service. Controlled volatility.

What is the general classification of automatic transmission fluids that includes Mercon and Dexron types?

Type F. Mercon/Dexron type. Synthetic ATF. High-frictional coefficient type.

Which of the following is considered a Static Seal component of the automatic transmission external components?

The extension housing seal. The transmission input shaft seal. The transmission oil pan gasket (seals stationary parts). The torque converter cover seal.

What component acts as a reservoir for transmission fluid, houses the transmission filter, and helps cool the fluid by having air flow over it?

The bell housing. The transmission case. The transmission oil pan. The extension housing.

The torque converter hub is the part of the converter housing that supports the rear of the converter. The outer surface of the hub provides a surface for which two transmission components?

The flexplate and the ring gear. The transmission front seal and bushing. The governor and the valve body. The stator support and the one-way clutch.

When a torque converter fails, which component is listed in Table 2 as a mandatory related sales opportunity?

Transmission mounts. Front pump bushing, front pump seal, and fluid. Oil pump O-ring seal. Stator support and stator one-way clutch.

When an oil pump fails, what component is listed in Table 2 as a recommended related sale item?

Torque converter drive lugs. Bell housing. Front pump bushing, front pump seal, front pump O-ring seal, and fluid. Governor cover.

What is the fundamental disadvantage of manually attempting to restart vortex flow by accelerating the engine after the vehicle has reached approximately 65 to 95 km/h (40 to 60 mph)?

The impeller speed will drop below the turbine speed. The stator will permanently lock to the stator support. The average-sized engine is generally not capable of restarting a strong vortex flow at those speeds. The clutch pack will engage automatically, preventing torque multiplication.

What non-transmission input signal is monitored by the PCM to determine the engine load, aiding in the application or release of the torque converter clutch?

Coolant Temperature Sensor (ECT). Vacuum Sensor (VS) signal (engine vacuum/load). Vehicle Speed Sensor (VSS). Throttle Position Sensor (TPS).

The greatest volume of oil discharged from the transmission oil pump is delivered to which primary component?

The lubrication circuit for the gear set unit. The external oil cooler. The torque converter. The hydraulic control valve system. Submit Answers