This Preliminary information communicates that a vibration concern on deceleration can be felt in the floor, seat, console and steering wheel between speeds of 70-60 MPH in 6th gear has been identified by G.M. If the clutch pedal is depressed and the concern is gone the likely cause is related to the transmission main shaft butIf the clutch is depressed and the concern remains the same or in 5th gear during the same speed range please continue with published vibration diagnosis in service information database.If a pico scope is used it presents at about 46 Hz. Technician is not to attempt any repairs at this time,a repair is being validated.
