Alternator pully? or loose alternator belt?
 

I have an 88 TII with a FD alt installed. Everytime I rev it up to 5k + on a low gear or neutral theres a loud nasty screech. I have pinpointed the sound to the alt, If i spray wd40 on the bearings of the alt pulley it'll go away for a minute but will eventually return. Any ideas guys? I was thinking a loose belt but maybe one of you can help.