Automatic Transmission Systems Flashcards

A vehicle with an automatic transmission is brought into the shop with the complaint of delayed engagement and the engine RPM flaring up during shifts. The technician confirms the fluid level is correct and the fluid is not burnt. Which of the following is the MOST likely cause of these symptoms?

Answer: Worn clutch packs or bands

When clutch packs or bands inside an automatic transmission are worn, they cannot create the necessary friction to engage gears properly. This results in the engine speed increasing without a corresponding increase in vehicle speed (flaring) and a noticeable delay before the gear engages.

What is the primary function of the torque converter's lock-up clutch in a modern automatic transmission?

Answer: To create a direct mechanical link between the engine and transmission at cruising speeds

The lock-up clutch engages at cruising speeds to eliminate the hydraulic slippage inherent in the torque converter. This creates a 1:1 mechanical connection between the engine's crankshaft and the transmission's input shaft, which improves fuel efficiency and reduces heat buildup.

The component in an automatic transmission that acts as the hydraulic control center, directing fluid pressure to apply clutches and bands, is known as the:

Answer: Valve body

The valve body is an intricate maze of channels, valves, and solenoids that directs high-pressure automatic transmission fluid to the correct clutch packs or bands at the precise moment to execute a gear shift.

A customer complains that their vehicle feels sluggish, shifts erratically, and the check engine light is on. A scan tool reveals a trouble code for a shift solenoid circuit malfunction. This indicates a likely problem with a(n):

Answer: Electro-hydraulic valve that controls fluid flow

A transmission solenoid is an electro-hydraulic valve that controls the flow of transmission fluid as directed by the Transmission Control Module (TCM). A circuit malfunction code points directly to an issue with the solenoid itself or its wiring, leading to symptoms like erratic shifting, harsh engagement, or the vehicle entering 'limp mode'.

Which of the following BEST describes the function of a planetary gear set in an automatic transmission?

Answer: It uses a sun gear, planet gears, and a ring gear to create various gear ratios.

Planetary gear sets are the core mechanical components that provide different gear ratios (e.g., reverse, neutral, forward reduction, direct drive, overdrive). By holding or driving different members of the set (sun gear, planet carrier, or ring gear), the transmission can achieve the various ratios needed for driving.

Automatic Transmission Fluid (ATF) serves multiple purposes. Besides lubrication and acting as a hydraulic fluid, what is another critical function of ATF?

Answer: To provide cooling and heat dissipation for transmission components

Automatic transmissions generate a significant amount of heat, especially in the torque converter. ATF circulates throughout the transmission and often through a cooler to dissipate this heat, preventing overheating and damage to internal components.