Driveshaft play in an 80q

[JShadzi at aol.com]

    Since I have owned the car it has always made kind of a "ching a link 
chink" sort of sound from the rear diff after hard acceleration and then 
letting off the gas and just coasting.  
    If I grab the driveshaft with the car sitting still I can turn it about 
30 degrees either way and it makes the same clinking sound.  It seems there 
is excessive play in the driveshaft.  Is this normal, what is on its way out 
it not?
Thanks,
Javad Shadzi
80qt