I don't know about being smarter but I fought the same issue so here goes.

The first thing I'd check is the downpipe to exhaust pipe connection. That's a tough leak to stop. I finally settled for just minimizing it as much as possible. If you have the old style downpipe and would like to upgrade it, I have one new in the box that needs a new home.

Then there's a possible cracked up-pipe and all the exhaust joint gaskets from the manifold up to the turbo.

That's some of the major exhaust leak culprits. If it turns out to be something to do with the all the emissions system, I'm jumping out as I have no knowledge of any of that stuff.

 

Get under the truck with a flashlight and start looking. Oil drips down and runs almost everywhere, blown by the air as you drive. If it's oil, there should be some traces somewhere. If you see nothing underneath, look from the topside.

 

From what you described it is very similar to a letter I recall getting in the mail from GM a few years ago. It was about a possible recall item dealing with the downpipe or some sort of cladding/heat shield by the down pipe.

I will try to find the letter but it describes small puffs of smoke, a possible burning smell from the area you described. If memory serves me correct the letter basically said if you experience these symptoms bring your vehicle to the dealer for repair and if not the warranty on the part was extended to 120k just in case symptoms become apparent.

Call up you local dealer and ask them about a recall/service bulletin.

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Thank you all for the replies. I will try to get underneath the truck and start looking at what you guys suggested, and put a call into my dealer next week.

 

I have a 2012 Silverado 2500HD in the shop at the very moment for broken exhaust pipe flange studs (for lack of a better term). These are the 4 studs just upstream from the DPF. It's underneath the cab, toward the passenger side, about even with the back edge of the front door.

The first stud broke about 6 months ago and a 3rd stud broke last weekend. Down to a single point of connection, I figured it was time to take action. LOL

After the second stud broke, the gasket bit the dust and I'd get the occasional whiff of smoke in the cab.

You may have a completely different leak, but that might be something to check.

 

Another thing to check is the down-pipe itself. They are cast by turbo connection with steel welded on farther down. Ive seen close to a handful with the steel broken off where welded to the cast.

 

If you can look back at the posts during 2012/13/14 or so timeframe there were many many posts and threads about this issue.

GM also did more than one bulletin about the problem.

You have a leak at the joint in the downpipe, and when it goes into regen (and the 9th injector is putting fuel into the exhaust stream) some fuel will be leaking at the joint and smoldering on the outside of the pipe.

I forget when the change was made in production, but the joint design was changed.

Some trucks had multiple problems with this issue -- some didn't have any.

 

Looking back at old posts from 2012-ish, I see what you mean! I guess I’m lucky it took nearly 10 years and 120k+ miles before this popped up for me!

 

Thanks again to all who replied. I will still look around and see what else I can find this weekend, but it sounds like a downpipe replacement is probably on my “to-do” list now. I’ll be browsing this forum for tips on that next; you guys are great! I appreciate the help!