the rear end started leaking

There is a grinding noise that starts when i let off the gas like slowing down or coasting. the thing is it feels like i have a 6 1/2 in lift 35x12.50s eaton posi k& n intake 4.56 gears slotted rotters 14 bolt rear and a TBI riser chip what do you think it is, and if i replace the rear end do i look for one already geard for my bigger tires or could this be something else. everything ive read talks about grinding when they gas it not when they let off the gas

thanks so much
Marni

ps im broke and i am having a hard time wondering how im gonna pay to fix it or id donate