NAPA - National Automotive Parts Association Certified Mechanic Automatic Transmission Systems Questions and Answers — Questions and Answers
Question 1: 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?
- A failing torque converter
- Worn clutch packs or bands (Correct answer)
- A malfunctioning valve body
- A clogged transmission filter
Correct 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.
Question 2: What is the primary function of the torque converter's lock-up clutch in a modern automatic transmission?
- To multiply engine torque during initial acceleration
- To allow the engine to idle while the vehicle is stopped in gear
- To create a direct mechanical link between the engine and transmission at cruising speeds (Correct answer)
- To absorb torsional vibrations from the engine
Correct 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.
Question 3: 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:
- Planetary gear set
- Governor
- Torque converter
- Valve body (Correct answer)
Correct 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.
Question 4: 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):
- Mechanical failure in the planetary gear set
- Electro-hydraulic valve that controls fluid flow (Correct answer)
- Worn out torque converter clutch
- Low automatic transmission fluid level
Correct 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'.
Question 5: Which of the following BEST describes the function of a planetary gear set in an automatic transmission?
- It acts as a fluid coupling to transfer power from the engine.
- It uses a sun gear, planet gears, and a ring gear to create various gear ratios. (Correct answer)
- It houses the solenoids that control hydraulic pressure.
- It filters contaminants from the automatic transmission fluid.
Correct 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.
Question 6: Automatic Transmission Fluid (ATF) serves multiple purposes. Besides lubrication and acting as a hydraulic fluid, what is another critical function of ATF?
- To increase the octane rating of the fuel
- To clean the fuel injectors
- To provide cooling and heat dissipation for transmission components (Correct answer)
- To generate electrical power for the solenoids
Correct 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.
NAPA - National Automotive Parts Association Certified Mechanic Automatic Transmission Systems Questions and Answers
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?