Driveshaft Play ? video included

[vinnY]

did it just happen or did you replace the shaft recently then this started happening?
first things i'd check is whether it's the right shaft
then check for a loose/missing hub nut
if all that checks out then go ahead and remove the shaft and check both inboard/outboard joints to see what's up
check if the C clip is still on the end of the shaft that goes into the box
if it happens to be the passenger side shaft and a b series, check that the intermediate shaft is bolted up to the engine block properly