grinding noise

i have a problem my jeep it has this grinding noise. it only happens when i take my foot off the gas at about 45 to 35 mph and then it's gone. i think it's coming from the rear but i'm not sure. i do have a locker in the front, but it was already installed when i got the jeep. any ideas? thanks for you time

Welcome to .
Sounds like backlash is set wrong on you rear ring and pinion.
If you belong to a local club, there is probably someone
skilled enough to inspect and set-up your R&P.
HTH

might want to check the u joints in your drive shafts, could be that simple.