unusual ticking noise when i reverse...?

[240!]

when i back up in my 90 240sx theres a funky ticking noise coming from the rear end... one of my budies said it could be my diff. but i personaly think its my right rear caliper. what do you guys think?

[HS13KLS]

id have to hear it...lol and is it TICKING or is it CLUNKING like loud?

[projekt_s13]

Do you have a welded diff?

Cuz i know mine and a few of my friends diffs click when reversing

[240!]

its more of a quiet clunking... lol

and my Diff is not welded