Purpose of Road Testing
The purpose of road testing is to duplicate the vibration complaint and to find any operating conditions that change or eliminate the vibration. Most importantly, road testing will determine whether the vibration is related to the engine speed or to the road speed.
In order to complete a quick and accurate road test, install an engine tachometer (such as a scan tool) and the EVA in the vehicle. Place the EVA vibration sensor in a location where the customer's concern can be felt.
Which Component Group is Causing the Vibration
After you have related a vibration to either the engine or to the vehicle-speed, break the vibration down further in order to fit into one of the following groups of rotating components:
| • | The engine, the clutch disc (manual transmission), the propeller shaft (within the driveline support assembly), the transmission flexplate (automatic transmission), and the transmission torque converter |
| • | The transmission output shaft and the rear axle differential pinion (mounted in the rear of the differential) |
| • | The tires, the wheels, the hubs, and the rotors |
These 3 groups represent the major areas that can produce vibration complaints. The components in each group are related to each other because the components are either bolted or splined together. This means that each group of components rotates at the exact same speed.
These categories can be broken down further in order to identify the exact component responsible for the disturbance. The emphasis is on testing (and more testing) in order to pinpoint the source and to eliminate unnecessary parts replacement.
Perform a road test for ALL vibration complaints unless the disturbance occurs only with the vehicle at a standstill.
