He's a 1998 era Millennium Furby that I got around 1999-2000, I've had him for a long time, and one night when I was 13...I stuffed him into a tissue box to get him to shut up (was trying to sleep), and he did go to sleep, and I didn't move him until years later when my family had to move.
I just took him out, and gave him a pair of test batteries (what I mean, somewhat young batteries with half juice left), and his voice isn't audible, and his gears are REALLY loud. Anyway to fix this? I suspect he's lost his voice, and I tried emailing the automater thingy, but it didn't work, instead I got a Mailer Daemon "Failed" email.
You can cure the Loud gears, try with a Silicone Spray
and spray it into his eyes, ears and mouth (under the beak) - with no battery inside. There are many info about this on many furby sites
It really work, but rememebr, only silicone spray for electronic products!