This is the exhaust setup on my 2007 Avalanche 5.3L Vortec (GMT900). I posted a quick sound clip so you can hear what a single MagnaFlow 5x8 14-inch muffler actually sounds like behind stock manifolds and gutted cats — no studio mic, just the truck running.
Clip here:
The setup
| Item | Setup |
|---|---|
| Truck | 2007 Chevy Avalanche |
| Engine | 5.3L Vortec |
| Manifolds | Stock |
| Cats | Gutted |
| O2 | Downstream non-foulers only |
| Muffler | MagnaFlow 12219 (5x8 oval) |
| Body length | 14-inch body / 20-inch overall |
| Inlet/outlet | 3-inch center/center |
| Factory pipe | ~2.75-inch, adapted to 3-inch |
| Tip | 4-inch rolled rear tip |
How it sounds
Louder than stock and deeper, but still controlled. The 14-inch 5x8 body keeps it from getting loud and droney, the gutted cats add the depth, and the stock manifolds keep the tone from going raspy. Daily-driver friendly — not obnoxious at cruise or sitting in a parking lot.
Want it louder?
Quick comparison if you are picking a muffler:
- 5x8 oval — most controlled, best daily-driver tone (what’s on my truck)
- 4x9 oval — louder middle ground, still muffled
- 4-inch round / glasspack-style — loudest and sharpest, more cold-start bark, most likely to drone
Downstream O2 note
The non-foulers are for the downstream/post-cat O2 sensors only. Do not put them on the upstream sensors — the PCM uses those for fueling. (And yes — gutted cats and O2 mods may not be road-legal in your area, so check local laws before copying this.)
Full breakdown + parts
Full write-up with pipe sizing, the muffler comparison, the O2 details and the parts links is on the site here:
Post your setup
Drop yours below so we can build a real list of what works on these trucks. Copy/paste and fill in:
- Truck/year:
- Engine:
- Muffler:
- Pipe size:
- Cats or no cats:
- Single or dual exit:
- Drone or no drone:
- Would you run it again?