Quick Answer: 2017–2019 L5P 5-Inch Dual Exhaust Install
On a 2017–2019 L5P Duramax, start the 5-inch dual system at the four-bolt front connection. Seat the front and intermediate hangers, position the Y-pipe and both rear branches, then measure the center extensions. The added driver-side tailpipe support and axle-area clearance must be correct before final tightening.
Before you start: Use this layout to sort the L5P rear pipes and check the added driver-side support mounting position. Confirm whether your wheelbase has the rubber mount required for the long-wheelbase hanger clamp before building the center route: 2017–2019 L5P 5-Inch Dual Exhaust Installation PDF.
Why Both L5P Outlets Must Be Aligned Together
Get both rear branches on their mounts before deciding that one tailpipe is too low. The splitter and center pipes affect both exits, so tightening one side early makes the other harder to align.
Sort the side-specific bends on the floor first. Then check the frame support, axle area and both outlets as one route, rather than treating each tip as a separate job.
U.S. emissions rules prohibit tampering with certified controls. A race-use label alone does not establish an exemption.
Match The 2017–2019 L5P Dual Layout
| Vehicle or layout check | What applies here |
|---|---|
| Truck covered | 2017–2019 Chevrolet/GMC 6.6L L5P Duramax. |
| Front connection | Four-bolt front connection; compare the actual flange before removal. |
| Rear route | 5-inch dual exit with separate driver and passenger rear pipe pairs. |
| Added support | Driver-side rear bracket uses the bottom hole in the illustrated layout. |
| Center support | Extra hanger clamp is used only on the long-wheelbase layout with a matching rubber isolator. |
Before You Remove Anything: This guide covers a 2017–2019 Chevrolet/GMC 6.6L L5P with a four-bolt front connection and a 5-inch downpipe-back dual route. Check the actual front flange, wheelbase and rear obstacles. A DPF-back kit starts farther rearward; its stock-pipe cut chart does not set extension length for this layout.
L5P Front Pipes, Splitter And Side-Specific Branches
| Component name | Illustrated manual reference | How to identify or fit it |
|---|---|---|
| Four-bolt front pipe | 11711 | Reuses the matching factory front hardware. |
| Intermediate pipe | 11252 | Seats in the stock rubber mount. |
| Center extensions | 50012 / 50018 | Select and size from the installed center gap. |
| Long-wheelbase hanger clamp | CH54 | Use only where the matching rubber support exists. |
| Y-pipe | Y500 | Splits the center route into left and right branches. |
| Driver-side over-axle pipe / tailpipe | 11764 / 11765 | Pairs with the added driver-side support. |
| Passenger-side over-axle pipe / tailpipe | 11762 / 11763 | Uses the matching passenger-side mounts. |
| Added driver-side hanger | H1 | The illustrated bracket uses its bottom hole. |
Use the shapes, pipe ends and welded supports in this drawing to match the components listed above.
Prepare To Support Two Rear Branches
Tip — Spare tire and hitch: The matching Flo-Pro four-bolt dual-route reference requires removal of the factory spare tire and its shield and excludes under-bed gooseneck hitches. These are restrictions of that specific route, not every L5P dual exhaust. Check them before removal; do not squeeze a conflicting branch against a tire or remove unrelated heat protection.
| Tool Or Equipment | What You Need It For |
|---|---|
| Stock removal | Use the equipment and tools in the truck-specific service procedure. Support each stock section before opening joints and releasing hangers. |
| New pipe installation | Sockets for the factory front fasteners, clamp tools and exhaust stands. Socket sizes are not listed in the kit PDF. |
| Extensions | Tape measure and cutting tools if required. Keep both rear branches supported during alignment. |
Start with a cold exhaust. Support the truck by the approved method and support each heavy pipe before release. Never work under a jack alone.
Phase 1: Establish The Front Route And Wheelbase Length
Installer Tip: Use long-wheelbase hanger clamp only for the long-wheelbase arrangement described in this kit manual, where the matching rubber mount is present.
Step 1: Support And Remove The Stock Exhaust
Start cold and support the heavy stock exhaust. Label electrical and pressure-line connections on the sections being removed. Undo the four front fasteners with the load supported. Open the remaining joints, release metal rods from the rubber isolators and lower each section in a controlled way. Keep the reusable front hardware and rubber supports.
Step 2: Fit The Four-Bolt Front Pipe
Seat the front pipe at the matching four-bolt connection with the original hardware. Place its hanger in the stock support and snug the fasteners while keeping the joint adjustable.
Step 3: Add The Intermediate Pipe
Join the intermediate pipe behind the front section and seat its hanger in the stock rubber isolator. Keep the pipe supported and the rubber free of sideways strain.
Step 4: Choose The Extension Layout
Trial-fit the center extensions without cutting. Their final length depends on the installed Y-pipe and rear branches. Leave the center loose now; return to mark any trim only after both outlets and all rear supports are positioned. The manual’s approximate connection allowance is not an instruction to add 5 inches at every end.
Step 5: Check The Long-Wheelbase Center Support
Use the extra hanger clamp only on the illustrated long-wheelbase arrangement with its matching stock rubber isolator. If that mount is absent, do not force the clamp into an unrelated frame hole.
Phase 2: Fit Both Rear Branches Before Setting Outlet Height
Step 6: Fit The Splitter And Driver-Side Axle Pipe
Fit the Y-pipe behind the trial center sections. Join the driver-side over-axle pipe to the driver outlet and seat the overhead stock hanger. Keep the splitter supported while locating both rear branches.
Step 7: Install The Added Driver-Side Support
Use the existing frame hole directly behind the driver-side upper shock mount. The illustrated added bracket uses its bottom hole, with the metal inside the frame and the rubber facing outward. Check behind the frame before placing hardware. Fit the driver tailpipe and seat its hanger.
Step 8: Fit The Passenger Branch
Join the passenger-side over-axle pipe to its Y-pipe outlet, then fit the matching passenger tailpipe. Seat the stock supports before setting outlet height. Keep both branches loose while comparing the exits.
Set Both Outlets Before Marking the Center Length
Level both outlets and support the Y-pipe. Measure the center gap with the front hangers and both rear branches seated. Check each actual insertion once; do not turn an approximate allowance into a fixed trim for every cab.
Shorten only a suitable plain end. Keep expanded sockets and welded hangers, deburr, then refit and confirm that neither rear branch pulls the splitter sideways.
Step 9: Level Both Exits And Tighten
Check brake lines, parking-brake cables and the axle vent tube. Once the route is right, tighten the front joint, then the right side and the left side. Use the proper hardware specs.
Troubleshoot A Low Outlet Or Missing Center Support
| What you find | What to check before changing parts |
|---|---|
| Driver outlet hangs low | Check the added bracket orientation and specified hole, then rotate the loose branch. Do not shorten the center pipe to cure a low rear support. |
| Extra hanger clamp has no rubber mount | It is conditional on the long-wheelbase support. Do not bolt it to an unrelated frame hole. |
| Pipe contacts the spare or hitch | Check the route-specific restrictions before tightening. A different extension length cannot cure an incompatible rear obstacle. |
Final Check: Two Supported Branches And Level Exits
- Added driver support: Bottom bracket hole at the illustrated location behind the upper shock mount; metal inside and rubber outward.
- Center support: Extra hanger clamp used only with the matching long-wheelbase rubber mount.
- Rear branches: Both side-specific over-axle/tailpipe pairs are supported and the outlets are level.
- Rear clearance: Brake lines, parking-brake cables, axle vent, spare-tire route and hitch restrictions checked before tightening.
Before use, have the joints checked for leaks with the proper shop method. Do not run the engine in a closed space. If there is a new rattle, soot trace or loose support, let the exhaust cool and correct the cause. Follow the supplied hardware maker’s heat-cycle recheck instructions.
For two exits on a 2017–2019 L5P, choose 2017-2019 / Dp-Back Dual / 5''. The link selects that version, rather than the 2020+ dual choices. View 2017-2019 / Dp-Back Dual / 5''
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Before Use: Calibration And Leak Checks
Arrange the compatible calibration and any device or service your exact package needs before use. Exhaust fitting does not include ECU programming. Diagnose warning lights, reduced power or leaks before operating the truck.
Conclusion
Seat the front and center supports, use the extra center hanger only where its matching rubber mount is present, then support both rear branches. Level the outlets and finish the center measurement before tightening.
For related parts on the same platform, browse L5P Duramax parts.
Choose The 2017–2019 L5P Dual Route
Use the vehicle and option table above to match your build. The collection includes other pipe sizes and layouts, so keep the exact option name with your parts list.
References
Flo-Pro four-bolt L5P dual-system reference — Cross-check the applicable support and routing notes; do not transfer another system’s cut lengths or hardware settings.
- SPEtuner: "ES08679S5.0 illustrated installation instructions." Available from SPEtuner installation PDF.
- U.S. Environmental Protection Agency: "EPA Fact Sheet re Aftermarket Defeat Devices and Tampering." Available from U.S. Environmental Protection Agency.
- Cover photo: "Dharmabumstead: "2018 Chevy Silverado Z71 2500 HD Midnight Edition.jpg — CC BY-SA 4.0. Layout added; vehicle photo retained. https://creativecommons.org/licenses/by-sa/4.0." Available from Cover photo: Dharmabumstead.
FAQ
Q: Which Hole Does The Added Driver-Side Support Use?
A: The illustrated L5P bracket uses its bottom hole at the frame location behind the driver-side upper shock mount.
Q: Does Every Truck Use The Extra Center Hanger Clamp?
A: No. The reference uses it only on the long-wheelbase arrangement with the matching rubber isolator.
Q: How Do I Identify The Driver-Side Rear Pipes?
A: Use the driver-side over-axle bend and matching tailpipe shown in the layout drawing. Check the hanger direction and added driver-side support before tightening.
Q: How Do I Identify The Passenger-Side Rear Pipes?
A: Match the passenger over-axle bend and tailpipe to the factory support route. They are a side-specific pair, not substitutes for the driver-side pieces.
Q: Can I Tighten The Right Side Before Fitting The Left?
A: Wait until both sides are fitted and aligned. Then follow the front, right and left tightening order.
Q: Will A Changed Spare Or Hitch Fit The Same Route?
A: Do not assume so. The matching reference route has specific spare-tire and under-bed hitch restrictions. Check those as well as tire and suspension clearance before using that layout.
Lars
Diesel Performance Engineer | 15+ Years Experience
"Empower Your Beast: Run Cooler, Pull Harder, Last Longer."
