DRIVETRAIN 411 DRIVETRAIN TROUBLESHOOTING AND DIAGNOSIS 1. Preliminary inspection Before performing a road test, preliminary actions can be taken to diagnose driveshaft noises. (a) Lift the vehicle on hoist. (b) Rotate the wheels and listen to”cluck-ing” noise while rotating wheels. (c) A “clucking” noise indicates a noisy driveshaft which needs to check and rectify. 2. Testing driveshaft noises Following points should be taken into account while performing a road test in order to diagnose driveshaft noises : (a) All the windows of the vehicle should be fully rolledup to reduce the disturbances caused by external noises. (b) Drive on a smooth road and pay particular attention to various noises emanating from the rear portion of the vehicle. Observe the changes in noise levels through speeds between 10 and 60 kmph. (c) It should be noted that the driver may encounter difficulty in distinguishing between similar noises resulting from either the drive shaft or from underbody (for example noise from strut) (d) Therefore, it is advised that the car be driven on uneven and bumpy surfaces as well, to observe the noises which may then be attributable to the underbody. (e) Tests for outboard (wheel side) and Inboard (engine side) joints are different and need to be conducted separately as given below. Checking for wheel side joint (OBJ) noise : NOTE : This noise will appear closer to the wheel, rather than the engine. (i) Shift to the 2nd gear and maintain a steady speed between 20 and 30 kmph. (ii) Drive the car to form a figure of “8” as shown in the figure 3. Identify an audible and persistent “Cluck” – like noise during either an extreme left or extreme right turn. (iii) The “Clucking” noise on a particular turn can be confirmed by repeating the turn. Checking for engine side joint (IBJ) noise : NOTE : This noise will appear closer to the engine, rather than the wheel. (i) Shift to the 4th gear and maintain a steady speed between 40 and 60 kmph. (ii) Lower the car speed by gently applying the brakes while ensuring that the tyres do not screech and the car does not dive forward. (iii) Identify an audible” Dug” sounding noise as the car decelerates. As the car slows down, it can be observed that the sound would become louder and occur after longer intervals.
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