A 1997 Dodge Grand Jielong MPV commercial vehicle. The owner reported that the vehicle body can clearly feel the left and right vibrations at a speed of 60km/h, and the front body feels particularly obvious. The vibration is more severe during the acceleration process, and the vibration changes when the accelerator pedal is pressed quickly. It is very violent, but if you slowly depress the accelerator pedal, the tremor will be lighter, and you can hardly feel it without depressing the accelerator pedal. Owners also reported that the vehicle is even more unbearable when the vehicle is heavily loaded uphill, but when the speed exceeds 70km/h, the vehicle can return to normal.
Fault diagnosis and troubleshooting
Judging from years of maintenance experience, this type of failure is mostly caused by the loosening of the suspension or the increased clearance of the hinged part, which causes vibration. When the vibration coincides with the vibration frequency of the vehicle body at a certain moment, the amplitude of the vibration increases, forming resonance . Raise the vehicle, check the chassis carefully, and use a crowbar to pry the rubber sleeves and ball heads. It is found that the ball head of the lower right control arm is slightly loose. After replacing the ball head, the problem improved slightly, but still exists:
The axial swing amount of the wheel exceeds the standard. This kind of situation will also occur. Remove the front wheel, re-balance it, and observe the car
The deflection of the wheel was found to be not serious, but two of the four wheels with lighter deflection were selected and installed on the front wheel, and tested again. The fault still exists.
Repeated testing and checking the chassis, but no valuable clues were found. It seems that the direction of thinking should be shifted. Will the vibration source of the vehicle come from the engine or the transmission and eventually be transmitted to the body? Raise the car, start the engine to rotate the front wheels, and keep the speed at 60km/h. At this time, under the car, you can clearly feel that the left and right swings of the engine and transmission are more severe than the body. After careful observation, it was found that the vibration source came from the left drive shaft. After turning off the car, shake the left drive shaft vigorously, and you can hear a "clam" sound. Therefore, it can be determined that the fault is caused by the excessive internal clearance of the ball cage in the drive shaft.
Disassemble the inner ball cage of the drive shaft and check that the inner ball cage is a star-shaped three-pin universal joint. The clip of the dust cover of the left inner ball cage drive shaft has been loosened, the grease has leaked out, and moisture has entered. Due to the long-term lack of grease lubrication, deep grooves have been worn out on the force-bearing side of the inner wall of the ball cage, and the needle rollers of the three small bearings have also escaped from the slide due to wear.
Because there are grooves on the inner wall of the ball cage, the expansion and contraction of the transmission shaft is restricted, which causes the engine to swing from side to side, which in turn causes the body to swing from side to side. When the vehicle speed is 60km/h, the frequency of the transmission shaft expansion and contraction overlaps with the natural frequency of the engine swinging through the engine support base, resulting in the largest amplitude of the vehicle shimmy; when the vehicle speed reaches 70km/h, the frequency of the transmission shaft expansion and contraction is related to the engine passing support The natural frequency of seat swing is quite different, so when the vehicle speed exceeds 70km/h, the swing phenomenon will disappear.
After replacing the left drive shaft assembly, troubleshooting.