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Need help with an aftermarket glasspack fitment


Jun 3, 2020
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Liberty Hill TX
I have a 2012 GMC Sierra 1500 with 2.75" exhaust pipe. I am wanting to delete my muffler and add a glasspack without welding. Problem is, I can't find any adapters to fit anything. Do I go with a 3" or a 2.5" glasspack? And whichever one I go with, what size adapters/reducers do I use? The muffler shops in this area charge around $350 for this work, so that's the reason for doing it myself. I appreciate any help given!!
The adapters will be the issue. If you can find something for adapters I would go with the 3" glasspack and reduce it down to the 2 3/4 pipes. Is it going to be a straight in and out? I don't recall what the muffler is like on the 12. Will any of the area shops make the adapters for you and then you can do the work yourself?
Unfortunately, that's the problem I'm finding is that it's not an easy in/out situation with the adapters. The closest I can get leaves about a 1/16" gap. Everything is so expensive in the Austin TX area and everyone wants to overcharge here. Any ideas on how to narrow the gap?
I just googled the 2 3/4 to 3" adapter and a bunch come up. I would use a 3" glasspack the length I want, a 2 3/4"ID to 3"OD adapter to adapt the pipe to the glasspack, then if needed a 3" pipe to get it to the tail pipe and a 3"ID to 2 3/4"ID to mate to the tail pipe. If you can't get everything you need this way then your off to the muffler shop.
The problem I'm having is that any 3" adapters, whether they are OD or ID aren't fitting around or in the glasspack I have. Am I looking at expanding the pipe a bit? Any suggestions on getting the adapters to fit?
First off, thank you so much for your advice. What do you think about the dynomax 17797 super turbo? I can get a great deal on it and it checks all the boxes. Let me know any opinions.
Looks like it will be the right size inlet and outlet for your truck, now is it the same length as the stock muffler?
I have Dynomax Super Turbos in two cars and I like the sound.
Like Scott said the inlet and outlet sizes are correct, but is the muffler length going to work, is the offset inlet and center outlet going to work? What is the muffler on the truck now like? Offset inlet and center outlet?