Trouble Diagnosis of Truck Drive Shaft

Observe the failure phenomenon

1. When the vehicle starts or shifts gears during driving, there is a crashing sound on the transmission shaft, especially when driving at a low speed in a high gear. The sound is more pronounced.

2. There is no abnormal noise on the drive shaft when the vehicle starts, but there is a crashing noise on the drive shaft when the vehicle is running.

3. There is no abnormal noise in the drive shaft when the vehicle starts, but there is abnormal noise in the transmission shaft when the vehicle is sliding.

4. The vehicle makes constant noise during the whole driving process.

Analyze the cause of the failure

1. The flange joints (or connecting bolts) of the drive shaft are loose, causing abnormal noise.

2. The grease nozzles and cross shaft oil passages are blocked and the grease cannot be injected, the grease is not filled on schedule, the cross shaft oil seal is damaged and the oil leaks, etc., which cause the cross shaft needle roller bearing to lack lubricating oil for a long time. Under work, the cross journal, needle roller and sleeve will become loose due to excessive abrasion and abnormal noise.

3. The assembly of universal cross shaft is too tight.

4. The sleeve and the universal joint fork hole are not closely matched, and the supporting piece bolts are loosened to cause the sleeve to rotate, which makes the universal joint fork hole excessively worn, loose and cause abnormal noise.

5. The spline of the second shaft of the transmission and the spline in the flange are worn too much, forming looseness and causing abnormal noise.

6. The fixing bolts of the intermediate support bracket of the transmission shaft are loose, the intermediate support is not tightly matched with the intermediate transmission shaft journal, the spline on the rear end of the intermediate transmission shaft is not tightly matched with the flange keyway, and the rear nut is loose.

7. The middle support bearing of the transmission shaft is loose, and the raceway of the bearing is damaged. The bearing is poorly lubricated and excessively worn.The intermediate support bearing of the transmission shaft is loose, the bearing raceway is damaged, the bearing is poorly lubricated, and the abrasion is excessive and loose.

8. The installation position of the intermediate support bracket of the drive shaft is skewed; the bearing pre-tightening is not adjusted properly; the rubber backing spacer is damaged; the tightening torque of the fixing bolts of the intermediate support bracket is too large or too small, which causes the position of the bracket to deviate.

9. The universal joint forks at both ends of the drive shaft are not in the same plane, which damages the constant velocity arrangement and causes abnormal noise.

Diagnose and troubleshoot

1. When the vehicle is running, the speed changes suddenly, and there is a metal knock on the transmission shaft, which can indicate that the individual flanges or universal joint cross shaft bearings are too worn and loose, causing abnormal noise of the transmission shaft.

2. The drive shaft makes a noise when the vehicle starts. When the vehicle is reversing backwards on a gentle slope, it makes intermittent noises, which can indicate that the needle roller is broken, and the needle bearing should be replaced.

3. When the vehicle starts or shifts gears, there is a noticeable metal impact sound on the transmission shaft. The low-speed gear is more pronounced than the high-speed gear. The interference fit between the inner ring of the intermediate support and the shaft is reduced and the looseness causes abnormal noise.

4. When the vehicle is starting or driving, the transmission shaft always has obvious abnormal noise and vibration, which means that the fixing bolts of the intermediate support bracket are loose.

5. When the vehicle is running at low speed, there is a crisp and rhythmic metal impact sound on the drive shaft, and there is a clear sound when the vehicle is sliding off the gear. Most of it is because the compression force of the universal joint bearing shell is too large, which makes the bearing unable to rotate flexibly.

6. When the vehicle is running, the sound of the transmission shaft increases with the increase of the vehicle speed. The intermediate support bearing emits a dull and continuous murky sound, which indicates that the intermediate support bearing falls apart due to excessive wear.

When the vehicle is running, the drive shaft emits a continuous "whee..." sound. First, check whether the fastening bolts of the intermediate support bearing bracket rubber gasket spacer sleeve are too tight or too loose (not in accordance with the specified tightening torque requirements), so that the bearing bracket is skewed.The tightness of the bearing cap bolts can be adjusted to eliminate abnormal noise. If there is still noise after adjusting the bearing pre-tightening, the lubrication condition of the bearing should be checked. If the bearing is poorly lubricated, the bearing should be removed and washed, and the bearing and bracket should be reinstalled after adding grease.

7. When the vehicle is running, the sound of the drive shaft is disorderly and irregular, and sometimes there is metal crashing sound, which means that the universal joint forks at both ends of the drive shaft are not in the same plane, which damages the constant velocity arrangement.

8. When the vehicle is running at a high speed, the transmission shaft has abnormal noise, and the abnormal noise of the transmission shaft still exists when the vehicle is sliding off. It is mostly because of damage to the raceway of the intermediate support bearing or the deviation of the installation position of the intermediate support bearing bracket.

9. In order to further verify the correctness of the above diagnosis, you can check and shake each part of the drive shaft when parking to see if the installation position is correct, whether there are any scars on the surface of the machine, whether the fastening connection is loose, and whether the matching gap is too loose or too tight.

•  Release the parking brake after stopping, and push the universal joint up and down by hand. If there is looseness, it means that the cross shaft needle roller bearing is loose.

   

• Shake the parking brake disc back and forth by hand. If there is looseness, it means that the spline of the second shaft of the transmission is loose.

• Tighten the parking brake and shake the rear flange of the intermediate drive shaft back and forth with your hands. If there is looseness, it means that the key teeth of the spline shaft of the intermediate transmission shaft are loose.

• Pull the flange of the intermediate drive shaft back and forth by hand. If there is looseness, it means that the nut on the rear end of the intermediate drive shaft is loose.

10. When the vehicle is running, if there is a heavy metal knock on the drive shaft when the brake is decelerated, it means that the rear leaf spring riding nut is loose.