Road Test
Road TestA road test is mandatory for any customer concern of noise/vibration that is not verified by the on-hoist check of chassis components. The Vehicle Road Test Evaluation form is arranged to record the conditions heard or felt during this test.
The road test form lists four operating conditions or modes in which some axle noises come and go: DRIVE, CRUISE, COAST, and FLOAT.
Operate the vehicle in all four modes and record those in which the noise occurs. Write down the kilometers-per-hour (miles-per-hour) range at which both noise and vibration occur. If equipped with four wheel drive (4WD), rear axle evaluations should be done on straight road sections only with 4WD lock engaged. The transfer case has similar construction to the rear differential. Both components exhibit similar noise characteristics. Axle noise can originate from either the transfer case or the rear differential. Using frequency analyzer evaluate vehicle between 60-80 mph. The transfer case will have objectionable noise frequency above 600 Hz. Rear differential will be below 600 Hz.
Vehicle Road Test Evaluation Form