ASE A2 key terms

A vibration felt during light-throttle cruising when the torque converter clutch applies and releases rapidly. Often caused by degraded fluid, a sticking TCC solenoid, or worn clutch lining.

The hydraulic pressure the transmission pump supplies to the hydraulic circuit. It rises with engine speed and load and provides the clamping force for clutches and bands.

A diagnostic procedure that holds the brakes, selects drive or reverse, and briefly opens the throttle to load the torque converter. Engine rpm at stall helps identify engine, converter, or clutch problems.

Connecting a gauge to a test port to read hydraulic pressure at idle, in gear, and under load. Comparing readings to specification helps locate pump, pressure regulator, or leakage faults.

The control strategy where the TCM adjusts shift timing and pressure based on observed clutch apply times, compensating for wear. Adaptives may need to be cleared and relearned after repairs.

A computer that monitors inputs such as speed, throttle, and temperature, then commands shift solenoids and line pressure. It also stores diagnostic codes and may share data with the engine controller.

A switch or sensor on the case that reports which range the driver selected, such as park, reverse, or drive. The TCM uses this signal to control starting, shifting, and reverse lamps.

An electrically operated valve that opens or closes a hydraulic passage, causing a specific upshift or downshift. A failed solenoid commonly produces a missing gear or a default to limp mode.

A solenoid that regulates hydraulic pressure by varying its duty cycle under computer command. It sets line pressure and shift feel, so a fault often causes harsh or slipping shifts.

A sensor that reports the rotational speed of the transmission output shaft or final drive. Comparing it with input speed lets the TCM detect slip, calculate gear ratio, and confirm shifts.

Unwanted relative motion between a clutch or band and its drum while the component should be fully applied. Slip raises engine speed without matching vehicle speed and can burn friction material.

A code stored by a control module when a monitored circuit or performance value falls outside its expected range. Codes are a starting point, not a diagnosis by themselves.

Live sensor and solenoid values displayed by a scan tool while the vehicle runs. Watching parameters such as slip, pressure commands, and ratio changes helps isolate faults that codes alone cannot.

The manufacturer's required fluid type, such as a specific automatic transmission fluid formulation, for a given transmission. Using the wrong fluid can change friction characteristics and cause shift complaints or internal damage.

Verifying automatic transmission fluid level with the engine running, transmission at operating temperature, and the selector in the specified range. Many units require checking in park with the engine idling.

Replacing most of the transmission's fluid using a machine or a drain-and-refill sequence. It removes contaminants and restores additive packages, but dirty fluid should not be used to mask a mechanical fault.

A screen or felt element that traps debris before fluid returns to the pump. It may be serviceable with the pan removed, and a clogged filter can cause low pressure and slipping.

Setting a band's apply clearance to specification using an adjusting screw or strut, usually with a torque-and-back-off procedure. Correct clearance prevents slip and delayed engagement.

Aligning the cable or rod between the shifter and the transmission so the indicated range matches the actual internal valve position. Misalignment can prevent starting or cause wrong-gear engagement.

Setting the cable that links the accelerator to the transmission so the valve body senses engine load. Incorrect adjustment raises or lowers line pressure and changes shift timing.

Running the engine and observing fluid flow from a disconnected cooler return line into a container. Weak or absent flow suggests a restricted cooler, kinked line, or failing pump.

The hydraulic control assembly bolted to the transmission case that routes fluid through spools, solenoids, and check valves to apply clutches and bands. It can often be serviced with the unit still in the vehicle.

A rubber-and-steel isolator that supports the transmission and limits its movement. A collapsed mount can cause clunks, misalignment, and stress on the case or driveshaft.

A lip seal that keeps fluid inside the case where the output shaft or half shaft exits. A worn seal lets fluid escape onto the ground or onto nearby components.

A heat exchanger, often built into the radiator, that removes heat from the automatic transmission fluid. A restricted cooler overheats fluid and can starve lubrication, so flow should be checked after a failure.

Reprogramming the transmission control module with updated calibration software, then performing the required drive cycle so adaptive values are relearned. Needed after some valve body or solenoid replacements.

Replacing or splicing damaged wires, terminals, and connectors that carry solenoid and sensor signals. Poor connections cause intermittent codes and erratic shifting that can mimic hydraulic faults.

A hydraulic cushion with a piston and spring that absorbs pressure spikes when a clutch or band applies. A worn accumulator seal or broken spring causes harsh engagement.

A group of gears consisting of a sun gear, a planet carrier with pinions, and an internal ring gear. Holding or driving different members produces the various gear ratios.

A set of alternating friction and steel plates that, when compressed by a piston, locks a rotating member to a drum. Clearance and plate condition determine holding ability and shift quality.

A flexible metal strap with friction lining that wraps a drum and tightens when a servo applies. It holds a reaction member for certain gears, and its clearance must be set correctly.

A fluid coupling with an impeller, turbine, and stator that multiplies engine torque at low speeds and transmits power to the transmission. It also drives the pump and houses the lockup clutch.

The engine-driven pump at the front of the transmission that pressurizes fluid for lubrication, cooling, and clutch apply. Worn gears or a damaged converter hub reduce pressure throughout the unit.

A mechanical device that locks rotation in one direction and freewheels in the other, holding a member during a gear. Rollers or sprags wear and can slip or seize.

Applying regulated compressed air to a hydraulic passage with the unit disassembled to confirm that a piston moves and a clutch or band applies. It also reveals leaking seals or cross-leaks.

The axial clearance between rotating parts and their thrust surfaces, measured with a dial indicator. Too little clearance binds parts; too much causes noise and misalignment.

Installing new sleeve bushings and roller or thrust bearings to restore shaft support and correct clearances. Worn bushings cause pressure loss, vibration, and gear noise.