probably the rear main (engine) seal is 'bad' . If the case then the transmission has to come out or seperated from the engine enough to repalce the seal. The seal itself is not a high dollar item. Most of the cost od this type of repair is labor
RepairPal Certified shops can diagnose and repair your 2001 Chevrolet Suburban 1500. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.