Bad vibration

I've got an 833 o/d in my swinger. In first and second especially during acceleration there little if any vibration. Third it gets worse on deceleration. Fourth gear it vibrates on acceleration and in coast it is in undrivable. Pushing the clutch in makes it a little better. Has anyone experienced this. Any thoughts or ideas would be greatly appreciated. I pulled it today, so its out of the car. Thanks

Well you might want to check your rear springs and axle U-bolts then.Cuz in 3rd and 4th gear, under coast, the pinion is yanked down by compression braking. If the u-bolts are loose or a spring is broken, voila.The pinion angle would go extreme.