ASE G1 Auto Maintenance and Light RepairManual Drive Train and AxlesMedium
A technician is diagnosing a complaint of excessive driveline vibration that intensifies with vehicle speed. Upon inspection, they notice that one of the driveshaft's universal joints (U-joints) has visible rust and appears stiff when articulated by hand. What is the MOST likely cause of the vibration?
- AWorn engine mounts
- BImproperly balanced wheels
- CSeized U-joint
- DDamaged transmission mount
Show answer & explanationAnswer & explanation
Correct answer: C. Seized U-joint
A seized or binding U-joint will cause the driveshaft to rotate unevenly, leading to a significant vibration that typically increases with vehicle speed. Rust and stiffness are clear indicators of a seized U-joint.
Why the other options are wrong
- A. Worn engine mounts can cause vibration, especially under acceleration or deceleration, but not usually a speed-dependent driveline vibration with a stiff U-joint.
- B. Improperly balanced wheels cause vibration, but it's usually felt through the steering wheel or seat, and not typically accompanied by a stiff U-joint.
- D. A damaged transmission mount can cause clunking or vibration, but a stiff U-joint points more directly to the U-joint itself.
Seized U-Joint Symptoms
A seized universal joint (U-joint) is one that has lost its ability to articulate freely, often due to lack of lubrication or corrosion. This causes driveline imbalance and vibration.
- Causes vibration that increases with vehicle speed.
- Can lead to clunking noises, especially when shifting or accelerating.
- Visually identifiable by rust, stiffness, or lack of grease.
- Requires replacement to restore smooth driveline operation.
Memory trick: Stiff U-joint, a vibration you'll feel, making the ride unreal.