How to Install Flowmaster Force II Cat-Back Exhaust - Single Side Exit (11-17 6.2L Sierra 1500) on your GMC Sierra

1) Disconnect the negative side of the battery cable. Raise the vehicle up on a hoist or rack to working height. If you do not have access to a hoist or rack, raise the vehicle and support securely with jack stands. Spray the nut on the clamped connection behind the catalytic converter and also the rubber mounts supporting the exhaust system with a penetrating lubricant. 

2) Support the muffler with a stand. Using a hacksaw or sawzall, cut the tailpipe just behind the muffler. Separate the three hangers on the tailpipe from the rubber mounts on the vehicle and lower the tailpipe from the vehicle. 

3) Loosen the clamp at the factory ball connection behind the catalytic converter using a deep 15mm socket and ratchet. Set the clamp aside, it will be reused in Step #1 of installation. Separate the hanger on the front pipe from the rubber mount on the vehicle and lower the muffler assembly from the vehicle.

1) Install the inlet pipe #36050S onto the factory ball connection and connect the hanger on the pipe to the rubber mount on the vehicle. Replace the factory clamp and tighten enough to hold in place, but still allow for adjustment. Check to make sure that the hanger is level and that the pipe runs true down the vehicle.

2) Place a provided 3½” clamp onto the inlet of muffler #853550-Z and place onto the back of inlet pipe #36050S. Support the muffler with a stand and tighten the clamp enough to hold, but still allow for adjustment. . Place the second 3½” clamp onto the muffler outlet.

3) Place tailpipe #36049S into its approximate position over the rear axle and connect the hangers on the pipe to the rubber mounts on the vehicle. Then slide the tailpipe into the muffler outlet. Tighten the clamp enough to hold, but still allow for adjustment.

4) Adjust the position of the pipes and muffler to provide a satisfactory fit. A minimum ¾” clearance around all parts of the system must be maintained while keeping suspension travel and vibration in mind. Be sure that the wire to the right rear wheel speed sensor is at least 1” away from the tailpipe to avoid damage to the wire.

5) Tighten down all clamped connections securely. After the system is secure, slide the ½” hanger keepers onto the ends of all of the hangers on the system. They will prevent the hangers from slipping out of the rubber mounts.

6) For a more secure installation, we recommend welding all slip-fit connections.