prop shaft , bad vibes.

Have just replaced all four ujs, now i am getting a shudder when decelerating at about 35mph. Seems to be coming from the front end. shaft ends were marked and put back same way round, if the prop has not gone on to diff and box same as they came off could this cause the vibration? if so any idea as to a cure. or do i need shafts balancing.
Thanks