You need to release the parking brake then take out two-thirds of the brake fluid from the master cylinder before replacing the rear Brake Disc. Lift the vehicle before dismounting the tire and wheel unit. Use wire to suspend the caliper and mounting bracket assembly as one unit from the suspension after you disconnect its bolts. Untwist the disc slowly while pulling it away from the axle center. Clean both sides of the wheel and axle hub before inserting the disc and twisting it into place toward the axle. Mount back the
Steering Knuckle assembly with the caliper and its holder. Clear away existing adhesive from the bolt threads before putting on new caliper mounting bracket bolts. Brush threads with brake parts cleaner until dry and let them dry naturally. Cover the bolt threads with gm threadlocker p/n 12345493 or red loctite product #272. Fasten the caliper mounting bracket bolts to the Steering Knuckle unit and torque them at 175 n.m (129 lb ft) for 15 series models while achieving 300 n.m (221 lb ft) for 25 series vehicles. Complete the process by installing the tire and wheel components, then take away the safety stands and lower the vehicle.