Yep, rear diff. The Ford dealer wanted 1000 just for the clutch pack replacement. The 900 is if the inner axle bearings are bad as well. He said it would be 500 for labor the other 400 would include the clutch packs and the inner bearings if needed. Is it a bad deal? This shop has done 15 of these compared with the other shops in town that haven't done very many or any at all.