Things You'll Need:
- New or used muffler
- Cardboard or a blanket
- Car jacks (optional)
- Wrench
- Sledge hammer
- Hacksaw
- Trash bag
-
Step 1
Verify you need a new muffler on your GMC Sierra by looking under the truck towards the back end to see if there are any large or small holes in the muffler or the muffler has fallen off partially or completely. Or, you may have determined it needs a new muffler because it's making loud grunting sounds or making gunshot sounds.
-
Step 2
Purchase a new or used muffler that corresponds to the year of your vehicle. It should have a 2.25-inch inlet and outlet diameter, a 4-inch X 9.75-inch X 13-inch case and a 19-inch overall case length. It should also have an offset-center design.
-
Step 3
Place an old blanket or a large piece of cardboard on the ground beneath the rear part of the GMC Sierra. This will allow you to replace the muffler comfortably without lying on the actual ground. You can also place the truck on a car jack if desired. If you use jacks, make sure you properly secure the truck on the jacks.
-
Step 4
Remove the old muffler. Completely loosen any bolts that are around the muffler and remove the muffler off. If the muffler is welded on, then you can break it away by knocking it with a sledge hammer. Dispose of the old muffler properly by breaking it down into small parts. Put the small parts in a trash bag.
-
Step 5
Replace the new muffler on your GMC Sierra. Line it up as straight as possible with the clamps and then tighten the bolts to hold it in place. The bolts should not be too tight because the muffler needs to move slightly to prevent damage. Make sure you hang the muffler with the hangers that come with it. If it does not have the hangers, then you may need to purchase them separately. Do not put it on too loosely or it may fall off.
-
Step 6
Start the engine and check the new muffler for any leaks or loud sounds. If there are leaks or loud sounds, then you may need to tighten the clamps tighter.
