Reinstalling stock cat - Chevy and GMC Duramax Diesel Forum
2011-2016 (Non Powertrain) Discussion of 2011-2016 topics not related to powertrain

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post #1 of 3 (permalink) Old 12-17-2019, 07:04 PM Thread Starter
Join Date: Jun 2019
Location: Martinez GA
Posts: 7
Reinstalling stock cat

For those of you that have reinstalled your stock cat after initially deleting it--how did you adapt the flange behind the stock cat to your "new" exhaust? I've looked but haven't been able to find an adapter made for this...
The pipe between the stock cat and the flange is kinda flattened so I don't think I can cut the flange off and mate my 5inch round pipe up to that flattened section.
Thanks, Rick
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post #2 of 3 (permalink) Old 12-17-2019, 07:19 PM
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Join Date: Apr 2018
Location: Cleveland GA
Posts: 50
I searched on line and found this still available:

I used it to adapt my muffler but it is 4inch pipe.

2015 Silverado 3500HD 4x4 LTZ 40 inch donaldson cat back exhaust
2007.5 Ram 2500 Sold
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post #3 of 3 (permalink) Old 12-17-2019, 08:15 PM
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Join Date: May 2007
Location: Rocky Top, USA
Posts: 7,195
Does your stock cat have a 4 bolt flange?
If so you should be able to get a 5 coupler with 4 bolt flange that should bolt right up.
Yes its a little larger but there should be enough meat to seal.
My 5 filter(less) back 3 bolt flange bolts up to my 4 - 3 bolt flange.
Start calling exhaust companies for flange adapters.
Better yet include some pictures of your project.
You can get 3 & 4 bolt flanges with or without pipe and make your own.
Maybe this will give you a few ideas.
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2007.5 GMC Sierra 3500 SRW L.B."BLACK" C.C. 4X4 LMM Z71
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