Tuesday, 15 October 2019

6 Indications Of A Failing Universal Joint

U-joints are components of the drive shaft assembly that are installed in most rear-wheel-drive trucks, four-wheel drive trucks, and SUVs or off-road vehicles. U-joints, which are in pairs on the drive shaft, compensate for height offset between the gearbox and rear axle while transmitting the power to move the vehicle. This allows each end of the drive shaft and associated universal joint to flex each time the drive shaft rotates to cope with misalignment.

Here are some symptoms
of a failing joint:

1. 
Squeaking sound when starting (forward or backward)

The bearing components of each universal joint are factory lubricated, but may not have a grease nipple to allow further lubrication after the vehicle is put into service, which limits the life of the vehicle. Since the bearing area of   each universal joint slightly twists with each revolution of the drive shaft, the grease can evaporate or be ejected from the bearing shell. The bearing becomes dry, the metal-to-metal contact is made and the U-pivot bearings squeak as the drive shaft rotates. The squeal is usually not heard when the vehicle is moving faster than 5 to 10 miles per hour due to other vehicle noise. The squeak is a sign that the universal joint should be serviced by a professional mechanic. In this way, you can extend the life of your existing U-joints.

2. 
When switching from driving to reverse, it rings

This noise usually indicates that the universal joint bearings have sufficient clearance to allow the drive shaft to rotate easily and then come to a standstill when power is reversed. This may be the next stage of deterioration if the bearings of the U-joint are not sufficiently greased. Maintaining or lubricating the U-joint bearings will not reverse the damage to the U-joint, but may extend the life of the U-joint.

3. 
Vibration feeling throughout the vehicle during forward motion at speed

This shake means that the universal joint bearings are now worn down enough for the drive shaft to move outside its normal rotational path, resulting in imbalance and vibration. This is a higher-frequency vibration than, for example, a wheel with imbalance, because the drive shaft rotates 3-4 times faster than the wheels. The worn universal joint now damages other vehicle components including the gearbox. The replacement of the universal joint by a specialist is certainly appropriate at this point to avoid further damage. Your mechanic should, if possible, select high-quality replacement U-joints with grease nipples to ensure long-term preventive maintenance and longer U-joint bearing life.

4. 
Transmission oil exits the rear of the transmission
Transmission fluid exiting the rear of the transmission is often due to a severely worn universal joint. The above-mentioned vibration has now worn the transmission tail shaft bushing and damaged the transmission output shaft seal, resulting in transmission oil leaking. If there is any suspicion that fluid is spilling out of the gearbox, the gearbox should be checked to determine the cause of the leak and a proper repair performed.

5. 
The vehicle can not move on its own; drive shaft offset

You've probably seen it before, a roadside truck with its drive shaft under the vehicle and no longer attached to the gearbox or rear axle. This is the ultimate failure mode for a universal joint , it breaks literally and drops the drive shaft on the sidewalk and no longer transfers power. The repair at this time includes much more than the universal joint and may require a complete drive shaft replacement or more.
 

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