ASE G1 Auto Maintenance and Light RepairManual Drive Train and AxlesMedium
A technician is inspecting a vehicle with a complaint of a clunking noise from the rear when accelerating from a stop or shifting gears. The noise is more prominent when towing. Upon inspection, the driveshaft U-joints appear to have excessive play. What is the MOST appropriate next action?
- ALubricate the U-joints and re-evaluate.
- BInspect the differential fluid level.
- CCheck the rear suspension bushings.
- DReplace the driveshaft U-joints.
Show answer & explanationAnswer & explanation
Correct answer: D. Replace the driveshaft U-joints.
Excessive play in U-joints is a direct cause of clunking noises during acceleration or gear changes, especially under load. Lubrication will not fix mechanical wear, and other components would typically produce different symptoms or be secondary concerns if U-joints are clearly faulty.
Why the other options are wrong
- A. Lubrication is for U-joints that are stiff or binding, not those with excessive mechanical play due to wear.
- B. Low differential fluid would likely cause whining or grinding noises, not clunking from play.
- C. Worn suspension bushings could cause clunking, but the primary inspection has already identified excessive U-joint play, making U-joint replacement the most direct and likely solution for the described symptoms.
U-Joint Play
Excessive movement or looseness in a universal joint, typically caused by worn needle bearings or cups, leading to driveline clunking noises.
- Causes clunking during acceleration/deceleration or gear shifts.
- Noise often more noticeable under load (e.g., towing).
- Requires replacement, not lubrication, once excessive play is present.
Memory trick: Clunking means something's loose, and U-joints are the usual culprits.