Finally got my Volant CAI installed, and am back to mulling over a muffler swap. I measured my pipes today and was surprised to find it calipered at
2.15" OD for the two pipes going in and 2.5" for the single pipe going out. Actually, one was 2.15 and the other was 2.21". I had thought I had 2 X 2.5" in and 1 X 3" out. Can anyone confirm that the 2008 QX56 was stock with the measurements I got today? I thought they changed both the Armada and QX56 pipes in 2007 to the larger size, which was why I was leaning to just a muffler swap. Pretty certain my system is OEM and hasn't been touched.

Everything I've read says I should have 2 X 2.5" pipes going into the muffler. But that's not the case. Can anyone comment or confirm? Anyone with an '07/08/09 model that can measure their pipes just before and just after the muffler? Or am I doing something wrong here?

I think you are all stock. The two pipes pipes before the Y are about 2 1/4". The tail pipe is 3" for a short distance at the outlet.

I think you are all stock. The two pipes pipes before the Y are about 2 1/4". The tail pipe is 3" for a short distance at the outlet.

We don't have a y pipe we have 2 pipes going in and 1 going out. The 2 going in are about 2.25 and the one going out is about 3"

We don't have a y pipe we have 2 pipes going in and 1 going out. The 2 going in are about 2.25 and the one going out is about 3"

The earlier Armadas had a Y pipe. I think they went to the two inlet muffler in 07.

YES! I have a Y-Pipe. What's a Y-Pipe?

Sorry, this post is absolutely of no use. I'm just worn to a plup from all the calls last night due to the snow. SLOW down when it snows people!

Again, sorry for hijacking - I'm going to bed.

We don't have a y pipe we have 2 pipes going in and 1 going out. The 2 going in are about 2.25 and the one going out is about 3"


Agreed. Except for the measurements. I thought we had 2 X 2.5" going in and 1 X 3" coming out of the muffler. I could see 2 X 2.25 instead of 2 X
2.5". But I'm not even getting 2.25" when I measure the pipes going in. I'm measuring 2.11 and 2.15". I had measured a little larger earlier, but that was right up near the muffler (the inlet itself, I think). Was only 2.15" a few inches away from the muffler. The pipe after the muffler only measures 2.65". I was pretty surprised by the measuremnents. Especially not seeing 2.5" in. Guess that was just bad info. Still surprised to not measure 2.25" on the inlet pipes. Is it that the inlets on the muffler are 2.25 and the pipes going in have to be just a little bit smaller than that to fit into the inlets?? Guess that would make sense.

After the muffler, I'm getting 2.65" on the single pipe out. But then it goes into a flange over the rear axle, and the pipe out of the flange is measuring 2.96". The tailpipe itself flares slightly to 3.07". So what size muffler would I need to order if I decide to only do a muffler swap?? 2 X 2.25" in obviously. But with the outlet pipe at 2.65" would I need a 2.5" outlet or a 3" outlet? I haven't seen anyone offering a 2.75" outlet. I only measured the pipe a few inches from the outlet side of the muffler. Guess I need to go back and measure the outlet itself.

Now the question is should I do catback or just muffler swap. From all I've read, the Armada/QX56 actually produces more HP/TQ with some backpressure. Going to 3" pipes will actually lose power. So I was just going to do the muffler swap. But I'm surprised by the small size of these pipes. Now I'm confused!! My local shop said it was a nightmare trying to add a catback on an 08 Armada they did a few months back, and they don't even want to do it (will, but don't want to). I don't have a lift available, so wouldn't try it myself. Which means going to a shop i don't really know anything about to do a catback. That alone makes me lean to muffler swap only. But those small pipes are bugging me.

FYI, I hadn't noticed it before, but they have a heat shield on one side of the pipe between the flange and the tailpipe. Obviously to protect the rear tire from the heat, as the pipe is pretty close to that rear tire. Anyone changing out those pipes probably should be sure to reinstall that heat shield.

As I stated, there are two exhaust system configurations. The 04-06s have a Y pipe; in 07 they have a dual inlet muffler. See attachments:

I have an 08' Armada. My factory tailpipe has an integrated resonator. Not at the tip, but where it loops up and over the lower control arm. What's interesting is neither of the above drawings shows that resonator. Curious if this was a running change.

Also note that my tailpipe broke off at the muffler flange and I rode around for a couple weeks without it. There was almost no difference in sound.

I may be wrong, but I think the Armada and QX56 had the in-line resonator added to quieten down the cabin. The drawing above is for the Titan. My guess is they didn't add the resonator to the Titan. I haven't even looked for mine. But pretty sure it being there has been confirmed several times by others. Which is why I hope to have no drone issues if I go with a Magnaflow muffler!

The tailpipe breaking at the flange has happened to several others. Poor job by the factory, it seems. Guess the welding robot needed reprogramming. Read on one of the forums that a guy had an $8000 (or something crazy like that) repair bill because of it. Don't recall the details, but most of it had nothing to do with the exhaust system.

Is it worth it to upgrade my '04 QX56 to the newer style? Will it improve power or mpg?

I'd like to upgrade my exhaust but don't want it to be louder than stock.