ASE G1 Auto Maintenance and Light RepairManual Drive Train and AxlesHard
A technician is diagnosing a loud whining noise that increases in pitch with vehicle speed, regardless of whether the vehicle is accelerating or decelerating. The noise seems to originate from the rear axle. This symptom MOST strongly suggests a problem with the:
- ASpider gears
- BWheel bearings
- CPinion bearing
- DAxle shafts
Show answer & explanationAnswer & explanation
Correct answer: C. Pinion bearing
A whining noise that changes with vehicle speed (not engine RPM) and is present during both acceleration and deceleration, originating from the differential, is a classic symptom of a worn or improperly adjusted pinion bearing. Wheel bearings would change with side loading, and spider gears typically cause noise only when turning.
Why the other options are wrong
- A. Spider gears are only active when the wheels are turning at different speeds (e.g., during a turn). They would not typically cause a continuous whine during straight-line driving.
- B. Wheel bearings cause a hum or growl that often changes with side loading (e.g., turning left or right), not necessarily a pitch change strictly with vehicle speed, and often not as pronounced or originating from the center of the axle.
- D. Axle shafts typically cause clicking or clunking noises, especially on turns, not a continuous whine.
Pinion Bearing Whine
A high-pitched whining or howling noise from the differential that changes pitch with vehicle speed, present during both acceleration and deceleration, indicating a worn or improperly adjusted pinion bearing.
- Noise changes with vehicle speed, not engine RPM.
- Present in both drive and coast conditions.
- Often indicative of worn bearing or incorrect bearing preload.
Memory trick: Whine and speed, front or back, pinion bearing's on the attack!