310T Drivetrain and Transmission 3 — Questions and Answers
Question 1: During a road test, a technician notices a clicking noise that occurs twice per driveshaft revolution only while turning. What is the MOST likely cause?
- Worn U-joint cross and bearings
- Worn constant velocity (CV) joint in the driveshaft (Correct answer)
- Loose companion flange bolts
- Excessive driveshaft runout
Correct answer: Worn constant velocity (CV) joint in the driveshaft
A worn CV joint produces a clicking noise during turns because the joint operates at an increased angle, revealing worn balls or races.
Question 2: What is the correct procedure when replacing a U-joint to prevent bearing cup damage during installation?
- Heat the yoke ears to expand them before pressing
- Press the bearing cups in simultaneously using an arbor press (Correct answer)
- Use only snap rings on one side of each yoke ear
- Drive cups in with a hammer and punch sequentially
Correct answer: Press the bearing cups in simultaneously using an arbor press
Using an arbor press to install both bearing cups simultaneously keeps the cross centered and prevents skewing the needle bearings.
Question 3: An Allison automatic transmission control module (TCM) stores a code for 'transmission range inhibit.' What does this indicate?
- The gear selector position sensor disagrees with the actual range selected (Correct answer)
- The transmission is operating above its maximum torque rating
- The cooler thermostat is stuck open
- The main regulator valve is sticking
Correct answer: The gear selector position sensor disagrees with the actual range selected
A range inhibit code is set when the TCM detects a mismatch between the requested gear range and the transmission's confirmed output range, often from a faulty selector or wiring issue.
Question 4: What is the MAXIMUM allowable driveshaft runout typically specified by most manufacturers for a heavy-duty truck driveshaft?
- 0.005 inches (0.13 mm)
- 0.025 inches (0.635 mm) (Correct answer)
- 0.060 inches (1.52 mm)
- 0.100 inches (2.54 mm)
Correct answer: 0.025 inches (0.635 mm)
Most heavy-truck manufacturers specify a maximum driveshaft runout of 0.025 inches (0.635 mm); beyond this, vibration and premature U-joint wear result.
Question 5: Which condition causes a manual transmission to become difficult to shift into any gear while the vehicle is stationary but easy to shift while rolling?
- Worn synchronizer rings
- A dragging clutch that does not fully release (Correct answer)
- Low transmission lubricant
- Bent shift forks
Correct answer: A dragging clutch that does not fully release
A dragging clutch continues to spin the input shaft after the pedal is depressed, making gear engagement difficult when the vehicle is stopped but easier when the output is already turning.
Question 6: In an Eaton Fuller 13-speed transmission, the auxiliary section provides which gear ranges?
- Low, Direct, and Overdrive
- Deep reduction, Low, and High
- Low and High splitter ratios (Correct answer)
- First through fourth auxiliary gears
Correct answer: Low and High splitter ratios
The Eaton Fuller auxiliary section provides a low and high splitter position that, combined with the main box, creates the full range of 13 forward speeds.
Question 7: A technician is checking driveshaft working angles and finds the front U-joint angle is 3° and the rear U-joint angle is 1°. What is the CORRECT action?
- This is within spec; no action needed
- Add a wedge shim under the transmission mount to equalize the angles
- Replace both U-joints immediately
- Add a wedge shim under the rear axle spring seat to equalize the angles (Correct answer)
Correct answer: Add a wedge shim under the rear axle spring seat to equalize the angles
For driveline cancellation to work properly, working angles at both ends of a driveshaft should be equal; a shim under the rear axle spring seat adjusts the pinion angle to match the front angle.
310T Drivetrain and Transmission 3
During a road test, a technician notices a clicking noise that occurs twice per driveshaft revolution only while turning.
What is the MOST likely cause?