Neutral Coast-Down Test

CAUTION: Refer to Road Test Caution in Service Precautions.

1. On a smooth level road, accelerate to a speed slightly higher than the speed at which the vibration occurs.
2. Shift the vehicle into NEUTRAL gear and coast down through the vibration range. Observe whether the vibration is present in NEUTRAL gear.
If the vibration still occurs in NEUTRAL gear, then the vibration is definitely sensitive to vehicle-speed. At this point, the following components have been eliminated as a cause of the vibration:
- The engine
- The clutch disc (manual transmission)
- The transmission flywheel (automatic transmission)
- The torque converter

Depending on the symptoms or the frequency, the repair will concentrate on one of the following components:
- The tire and wheel assemblies
- The transmission output shaft
- The propeller shaft
- The rear axle differential pinion
- The rear drive axle or the rear drive axle shafts