Download This is a higher-frequency, lower-amplitude vibration than high-speed shake, directly related to road speed, and usually more noticeable at higher road speeds, 72 km/h (45 mph) and up. It is felt in the floor pan or heard as a rumble, hum or boom. It will exist in all drive modes, but may vary somewhat in acceleration, deceleration, float or coast modes. If the vibration is particularly responsive to heavy acceleration or deceleration, especially at lower speeds, driveline angles should be checked. A driveline vibration can usually be duplicated with the axle supported on a hoist or jack stands; through light brake application while accelerating and decelerating, to simulate road load resistance, may be necessary to bring it out. 1. Raise vehicle promptly after road-testing, on twin post hoist or jack stands, to prevent tire flat- spotting. Engage drive train and run-up to observed road test speed to verify presence of vibration. If not evident, check non-driving wheels with wheel-balancer spinner to rule out imbalance as a possible cause.