whats the squeaking under my truck?

i have a x reg ford transit pick up lwb and theres a noise underneathwhen i reverse more than going forward,i thought maybe the centre bearing rubber on way out as it sounds like a rubbery squeak but when i dip clutch noise disappears,centrebearing etc ok but now looking at transmittion clutch gearbox possible axle twin wheel type, any suggestions

wayne
September 2008