2007.5-2010 GMC Duramax LMM Downpipes

Matching a down pipe to the turbo on your 2007.5-2010 GMC Sierra HD

Pick the pipe by its turbine-housing end before anything else. The LMM left the factory with a water-cooled Garrett GT3788VA variable-vane turbo, and the 3 in stainless pipes listed for 2004.5-2010 and 2001-2016 Duramax trucks bolt to that housing. If somebody has already fitted an S300-style charger or a twin-turbo arrangement, a stock-pattern pipe is simply the wrong part, which is why separate pipes are listed for those builds. Past the flange the job is the same for all of them: the pipe hangs off a support bracket and hands the gas to the diesel oxidation catalyst and the particulate filter behind it.

Why these pipes and their joints give trouble

The pipe itself rarely wears out. The connections do. GM used aluminized stainless here, and the two flanges plus the clamp spend their life being pushed around by an engine that moves and a frame-mounted exhaust that does not. A missing support bracket, a flattened lower flange gasket or a clamp that worked loose all read the same way from the driver's seat: a tick that shows up under load, with soot drawn around the joint. Because the leak is upstream of the filter, it commonly throws off the pressure and temperature sensors as well, and the truck answers with regens it did not need. Keep in mind that the cast manifolds and the passenger-side up-pipe bellows ahead of the turbo crack on heat cycles rather than at a published mileage, and they can be the real source of the noise you are chasing.

Stock diameter or a 3 in upgrade

If the pipe is rusted through, cracked, or missing the bracket that holds it, a straight replacement is the whole job and the truck goes back to how GM built it. A 3 in stainless pipe for the factory turbo is the step most Sierra owners take instead, and it changes nothing about the aftertreatment: the oxidation catalyst and the particulate filter stay bolted exactly where they were, and the pipe only gives the turbine a cleaner, better-sealed path into them. For a truck already running a different charger, the matching pipe is less an upgrade than the only thing that will bolt up. Order fresh flange gaskets and the support brackets alongside whichever one you choose.

Pipes and parts in this group

Start with the swapped-turbo builds, since those are the hardest to shop for: Wehrli Custom Fabrication lists a 3 in S300 down pipe for 2004.5-2010 engines and a 4 in twin-turbo down pipe covering 2001-2010 6.6L trucks. For a Sierra on the stock charger, PPE has a 3 in stainless downpipe spanning 2004.5-2010 and MBRP an Armor Lite 3 in turbo downpipe spanning 2001-2016. Treat the remaining PPE parts as the repair kit that goes with any of them: downpipe support brackets and the lower flange gasket. Everything in this group drops into the stock exhaust path with the catalyst and filter still in service.

Fitment notes for the Sierra HD

Two questions settle most down pipe orders on these trucks: what turbo is bolted to it, and what body is under it. The Sierra HD came in work truck, SLE and SLT trim as a regular cab with the long box, an extended cab with either box and a crew cab with either box, 133 to 167 in of wheelbase, so even though the down pipe sits ahead of those length splits, the system it joins does not. A 2007 Sierra Classic is the previous body with the LBZ rather than an LMM truck. Parts built for the 2011 and newer LML, the 3 in down pipe included, do not carry back here. Run the VIN through the fitment checker on the product page if any of that is unsettled.

Frequently asked questions

My Sierra has an aftermarket turbo. Which down pipe fits?

Order by the turbine housing, not by the model year. A pipe cut for the factory variable-vane turbo will not line up with an S300-style charger or a twin-turbo arrangement, which is why the 3 in and 4 in pipes for those builds are listed separately. If you are not certain what is on the truck, call the shop and describe the charger.

Does a 3 in pipe make the particulate filter work harder?

No. The pipe ends where the oxidation catalyst begins, so the aftertreatment is untouched and keeps regenerating the way GM set it up. What does change regen behavior is a leak, so seal the flanges properly when the new pipe goes in.

Is a V-band clamp included?

Aftermarket 3 in systems join the down pipe to the front pipe with a V-band clamp, but what actually ships in the box varies by part, so read the listing before the truck is in the air. Flange gaskets and support brackets for this engine are listed here if something comes up short.

It ticks under load since the new pipe went on. Now what?

Start at the flanges you just opened, because a reused gasket or a bolt that never came back to torque leaks exactly like that. If those joints are clean, work further up to the manifolds and the passenger-side up-pipe bellows, which crack with age and heat cycling and sound much the same from the cab.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.