DTC DTC Drivetrain and Transmission Systems 2

Question 1

What is the primary function of a differential in a diesel truck's drive axle?

Accepted Answer

To allow drive wheels to rotate at different speeds during turns

Answer

The differential allows the inner and outer drive wheels to rotate at different speeds while still receiving engine torque, preventing tire scrub during cornering.

Question 2

Which fluid is typically used in heavy-duty diesel truck manual transmissions?

Accepted Answer

Gear oil (GL-4 or GL-5)

Answer

Heavy-duty manual transmissions use gear oil rated GL-4 or GL-5 to lubricate gears, bearings, and synchronizers.

Question 3

A diesel technician notices a differential whine that increases with vehicle speed but disappears when coasting. What is the most likely cause?

Accepted Answer

Pinion gear bearing wear

Answer

Pinion bearing wear typically produces a load-dependent whine that is most pronounced under acceleration and quiets during coast when load is reduced.

Question 4

What is the purpose of a limited-slip differential (LSD) in a diesel work truck?

Accepted Answer

To transfer torque to the wheel with more traction when one wheel slips

Answer

A limited-slip differential uses clutch packs or a locking mechanism to bias torque toward the wheel with the most traction, improving off-road and low-traction performance.

Question 5

During a transmission service on a heavy-duty diesel, what is the correct procedure for checking fluid level in a manual transmission?

Accepted Answer

Remove the fill plug; fluid should be at the bottom of the fill hole thread

Answer

Manual transmissions use a fill plug on the side of the case; fluid should be level with the bottom of the fill hole opening to indicate a proper fill.

DTC - Diesel Technician Certification Practice Test

DTC - Diesel Technician Certification Practice Test

DTC DTC Drivetrain and Transmission Systems 2