Vibration at Deceleration

This is classic pinion angle grief.
Under deceleration, engine compression is yanking the pinion nose down. So either the springs are soft (unlikely), the tranny mount is torn (possible),or loose, or the pinion angle needs checking and/or readjusting (most likely).There's also a slim chance that; one or more U-joints is loose or that the driveshaft is too short.http://www.drivelineserviceofpittsbu...-do-you-need-1