A2 Automatic Transmission Practice Questions

Explanation: A stall test measures engine speed at full throttle with the brakes applied and transmission in gear. A lower than normal stall speed indicates the torque converter lockup clutch is not fully engaging or the engine lacks power. This is different from a high stall speed, which would indicate a slipping stator clutch.

Explanation: The stator in the torque converter redirects fluid returning from the turbine back toward the pump, multiplying torque input. This torque multiplication is what allows the transmission to accelerate the vehicle from a standstill. Once the turbine speed approaches pump speed, the stator freewheels and torque multiplication ends.

Explanation: A 2-3 upshift involves releasing one component (band or clutch) and engaging another. Slipping during this shift typically indicates the engaged component is worn and cannot hold. The 3rd gear clutch or band that should engage is likely worn. A faulty solenoid would prevent proper shift timing rather than cause slipping.

Explanation: The transmission cooler is mounted in the radiator lower tank or as an external unit and cools hot transmission fluid returning from the transmission. Proper fluid temperature is essential for friction material performance, seal life, and component longevity. Most coolers are integrated into the engine cooling system.

Explanation: Low pressure in all ranges indicates a system-wide issue: low fluid level, worn pump, or blockage. Before replacing components, verify fluid level and condition (burnt fluid indicates overheating and friction material breakdown). A worn pump or blocked filter would require internal service.

Explanation: A harsh 1-2 shift often results from improper solenoid timing (too quick engagement) or inadequate pressure modulation. The 1-2 shift solenoid controls when hydraulic pressure is applied to execute this shift. A faulty solenoid or wiring can cause harsh shifts or shift delays.

Explanation: The lockup clutch mechanically couples the turbine to the pump at higher vehicle speeds, eliminating fluid slip and improving fuel economy. When disengaged, the converter provides torque multiplication at low speeds. Lockup is controlled by the transmission control module (TCM) based on speed and load conditions.

Explanation: A stuck shift solenoid is the most common cause of no upshift with no TCM codes. The solenoid may be mechanically stuck or have electrical resistance preventing proper operation. A failed speed sensor would typically set a code. Check solenoid resistance and vacuum/hydraulic operation.

Explanation: A faulty stator one-way clutch that slips (freewheels) in both directions eliminates torque multiplication. This results in very high stall speed because the engine can spin faster before building sufficient torque to move the vehicle. The opposite (very low stall speed) indicates weak engine power or a slipping lockup clutch.

Explanation: Under towing loads, heat generation increases. If the cooler is blocked (by debris or mineral deposits), coolant cannot flow through it to cool the fluid. This is especially problematic if the cooler is mounted in the radiator lower tank where it may accumulate particles. Check cooler flow and flush if necessary.

Explanation: Before removing the valve body, photograph all solenoid connector positions and any check balls or springs. The valve body contains precisely positioned components. Documentation prevents assembly errors that can cause shift problems, pressure issues, or complete transmission failure.

Explanation: Burnt-smelling, dark transmission fluid indicates thermal breakdown of the oil and friction material failure. This results from sustained overheating, often due to cooler blockage or heavy towing without adequate cooling. The cause must be corrected and internal transmission damage assessed.

Explanation: An input speed sensor reading of zero while the transmission is loaded indicates either sensor failure, wiring issues, or a mechanical problem (broken input shaft, planetary lockup). The sensor should read engine RPM in gear. Check sensor resistance, wiring, and verify shaft rotation.

Explanation: Transmission fluid is multifunctional: it provides hydraulic pressure for clutch and band operation, cools the transmission, lubricates all moving parts, and protects against corrosion. The friction material properties are critical for proper clutch feel and wear life. Fluid selection is important for transmission longevity.

Explanation: Delayed engagement when shifting into Drive typically indicates a slipping forward clutch. The clutch takes time to build friction and engage, causing a hesitation before vehicle movement. This is different from clunking engagement, which often indicates worn engine mounts or drivetrain free-play.

Explanation: The transmission pump is a gear pump driven by the torque converter hub, pressurizing fluid from the sump. This pressurized fluid operates all hydraulic valves, solenoids, clutches, and bands. Pump output capacity and pressure are critical for transmission operation.

Explanation: A bent sun gear or reaction member must be replaced, not straightened. These components must maintain precise tolerances and concentricity for proper planetary gear set function. Attempting to straighten will not restore precision, and the component will fail again under load.

Explanation: No reverse with normal forward operation indicates a worn or slipping reverse band or reverse clutch. Reverse is typically a direct apply without complex ratio changes. Fluid level affects all gears, not just reverse. A switch issue would not prevent mechanical reverse operation.

Explanation: Check balls are spring-loaded one-way valves embedded in the valve body that direct fluid flow to specific circuits and prevent backflow. They are critical for proper shift sequencing and pressure routing. Displacement or loss of a check ball causes severe transmission problems.

Explanation: Cold transmission fluid is thicker, reducing flow rate and hydraulic responsiveness. Shifts are softer (less firm) until fluid warms and thins to operating temperature. This is normal behavior. Using incorrect fluid viscosity for the climate can exacerbate this issue. Once the transmission reaches operating temperature, shifts should normalize.

Explanation: The output speed sensor provides vehicle speed feedback to the TCM for shift timing decisions. An intermittent signal causes the TCM to receive conflicting information about vehicle speed, resulting in erratic shift points, delayed shifts, harsh shifts, or limp mode engagement if a sensor code sets.

Explanation: Transmission whining is most often caused by a worn pump with increased internal clearance, creating cavitation or gear noise. It can also indicate worn planetary gear sets or damaged thrust washers. The noise increases with engine speed and indicates internal wear requiring service.

Explanation: P0700 is a generic code indicating transmission problems exist but not specifying the fault. The TCM must be scanned for transmission-specific codes (P0715, P0730, etc.) to identify the actual problem. Different manufacturers store transmission codes differently, so proper diagnostic equipment is essential.

Explanation: The pressure relief valve opens when hydraulic pressure exceeds its set point, allowing excess fluid to return to the sump. This protects hydraulic components (seals, cylinders, clutches) from overpressure damage. Relief valve setting directly affects shift feel and system durability.

Explanation: Shuddering during lockup indicates the clutch is not engaging smoothly, typically from worn friction material or solenoid malfunction preventing gradual engagement. Normal lockup is smooth. The solenoid or lockup clutch (stator) requires inspection and likely replacement.

Explanation: A transmission band is a brake component consisting of friction material around a drum attached to a planetary gear member. When hydraulically applied through a servo, it stops rotation of that gear member, creating a specific gear ratio. Different band applications (2-3 band, low-reverse band) control different gears.

Explanation: A spun bushing indicates bearing failure causing shaft movement. The bushing must be removed and replaced with the correct part. Bushings are precision press-fit components. A spun bushing will cause continued bearing damage and eventual shaft binding. Proper installation is critical.

Explanation: Shift points are determined by vehicle speed and load. If the speed sensor provides inconsistent readings, the TCM receives conflicting information about when to shift. Erratic shifts result. Verify sensor output and wiring before blaming the TCM.

Explanation: The modulator is a mechanical vacuum-actuated device that adjusts transmission line pressure based on engine load. Low manifold vacuum (high load) increases pressure for firmer shifts. High vacuum (light load) reduces pressure for softer shifts. Modern transmissions use electronic pressure management instead.

Explanation: A clogged filter restricts fluid flow, reducing hydraulic pressure. Low pressure cannot engage clutches and bands properly, causing slipping. Slipping generates heat (friction), rapidly degrading fluid and friction materials, leading to transmission failure if not corrected immediately.

Explanation: A cracked piston can fail under pressure, causing fluid leakage and clutch failure. The piston cannot be reliably repaired. The entire clutch pack should be replaced to ensure reliability. Temporary repairs on critical hydraulic components are unacceptable.

Explanation: One-way clutches (overrunning clutches) are mechanical devices that allow free rotation in one direction but lock in the opposite direction. They are used in planetary gear sets to prevent reverse rotation of specific gear members, establishing the desired gear ratios and shift sequences.

Explanation: Park is a mechanical lock, not a hydraulic function. A broken park pawl or damaged linkage between the shift lever and pawl prevents the pawl from engaging and locking the output shaft. The vehicle cannot be safely parked and must be repaired immediately.

Explanation: High water content in transmission fluid indicates a leak in the transmission cooler (located in the radiator), allowing engine coolant to contaminate the transmission fluid. This is a serious condition. The cooler must be flushed or replaced, and contaminated fluid changed immediately.

Explanation: An ohmmeter test only checks solenoid coil resistance. It doesn't verify actual operation, wiring integrity, or voltage supply. A solenoid with good resistance may still fail due to poor connections, corroded terminals, or inadequate voltage. Check the entire circuit before replacing the solenoid.

Explanation: The pump intake must draw fluid from the sump freely. A blocked intake (from sludge, filter restriction, or debris) reduces pump output, lowering line pressure. Low pressure causes slipping of all engage elements and rapid heat generation, destroying the transmission.

Explanation: A clunk when shifting into Reverse (or Drive) typically results from driveline slack being suddenly taken up when the transmission engages. Worn U-joints, CV joints, motor mounts, or transmission mounts can allow excessive free play. This is a driveline issue, not always a transmission problem.

Explanation: Pressure varying between gears indicates a specific hydraulic control problem, not a pump issue. Reverse having low pressure while forward gears are normal suggests a blockage in the Reverse pressure circuit, a broken return spring in a servo, or the pressure regulator not responding properly for that range.

Explanation: ATF specifications vary because different transmission designs use different friction material, plate materials, and valve designs requiring specific fluid properties. Using incorrect fluid can result in slipping, harsh shifts, poor cooling, and transmission damage. Always use OEM-specified fluid.

Explanation: A partially blocked cooler line restricts coolant flow through the cooler, reducing cooling efficiency. During high-load situations (towing), the transmission cannot shed heat adequately and overheats. This causes fluid breakdown and friction material failure. The line must be flushed or replaced.

Explanation: Planetary gear sets require precise clearances. Excessive clearance causes noise and improper power transfer. Insufficient clearance causes binding or locking. Shim selection must achieve the correct clearance specification. Improper clearance leads to transmission failure.

Explanation: Severe shudder during acceleration across all gears points to an engine problem (misfire, spark knock) rather than transmission wear. Engine misfires cause torque interruptions that feel like transmission slipping. Diagnosis should include ignition system and fuel system checks before transmission overhaul.

Explanation: The dipstick indicates fluid level (must be within specification for proper transmission operation and cooling) and allows visual inspection for contamination, burnt odor, or discoloration indicating problems. Checking the dipstick is the first diagnostic step for transmission issues.

Explanation: A stuck check ball indicates varnish buildup or contamination in the valve body. The ball must be carefully freed, the cavity cleaned thoroughly, and the cause of the contamination identified. The rest of the valve body must be inspected. Ignoring this will cause the same problem immediately after assembly.

Explanation: Reverse requires higher pressure than forward gears because it directly applies the reverse clutch or band without ratio reduction. Pressure specification is provided by the manufacturer. The pressure relief valve is calibrated for this requirement.

Explanation: The pressure regulator is designed to increase line pressure with throttle opening (engine load) for firmer shifts during acceleration. This is normal operation. The pressure is modulated between idle and wide-open throttle. Excessive pressure beyond specification indicates a regulator malfunction.

Explanation: Cold fluid is thicker and flows more slowly through valve passages, delaying hydraulic response. Once the transmission warms, fluid viscosity decreases, flow improves, and shift timing normalizes. This is expected behavior. Using the correct fluid viscosity for climate conditions minimizes this issue.

Explanation: Pan gaskets are designed specifically for each transmission model. Incorrect gaskets may not seal properly, may pinch and leak, or may have incorrect fluid hole positions. Always use OEM-specification gaskets to ensure reliable sealing and prevent costly transmission fluid loss.

Explanation: Gear hunting (rapid upshift and downshift cycling) indicates the TCM cannot determine actual vehicle speed accurately. An intermittent or faulty output speed sensor is the most likely cause. The TCM sees alternating speed signals and cannot stabilize on a gear. Verify sensor output and wiring.

Explanation: Servo return springs force the servo piston to release when hydraulic pressure is exhausted. Without functioning springs, the servo cannot release, keeping the band applied. This prevents proper upshifts and locks the transmission in an incorrect gear. Springs must be installed and functional.

Explanation: Thrust washers are placed at specific locations to limit axial (along the shaft centerline) movement of gears, planetary sets, and shafts. Proper selection ensures correct clearances. Worn thrust washers cause internal contact, noise, and eventual component damage.

Explanation: Noise from the torque converter typically indicates internal wear: damaged turbine or stator bearings, worn pump gears, or broken vanes. These components cannot be repaired and the converter must be replaced. The noise increases with engine speed and load.

Explanation: Contamination in a rebuilt transmission will cause immediate failure. All components must be thoroughly cleaned to remove old fluid, metal particles, varnish, and contaminants. The transmission case must be cleaned inside and out. Only clean parts should be assembled.

Explanation: Burnt fluid after a rebuild indicates internal slipping, typically from improper assembly (incorrect band/clutch application, check ball misplacement) or component installation errors. The rapid heat generation indicates serious problems. The transmission must be removed and the problem identified.

Explanation: Transmission solenoids are position-specific. Installing them in wrong locations or with reversed connectors causes transmission malfunction. Before removal, photograph positions, mark connectors, or use a service manual diagram. Incorrect installation will result in shift problems requiring repeat disassembly.