(Used) 1991 GMC C7000 Topkick, COMPLETE DIFFERENTIAL HOUSING ONLY- Part Number: 15566578, Serial Number: H902638136, Make: Eaton, Model: 21065T, Ratio: 4.11, Capacity: 21,000 Lbs, For more information about this item, give us a call. We ship Worldwide! (CRG HEAVY TRUCK PARTS) 929 W PULASKI HWY ELKTON, MD 21921