Quick Answer: 2015.5–2016 LML 5-Inch Dual Exhaust Install
For the 2015.5–2016 LML 5-inch dual route, match the three-bolt front connection first. Refit the transmission-mounted hanger bracket with the new front pipe, add the intermediate support, then hang the Y-pipe and rear branches. Measure the center extensions only after the hangers and outlets are positioned.
Before you start: Pay close attention to the retained transmission bracket and its upper rubber hole. The late-LML illustrations also show the center support and added driver-side support mount used by this dual system: 2015.5–2016 LML 5-Inch Dual Exhaust Installation PDF.
Why A Late-LML Rear Fit Problem Can Start At The Front
On a late-LML dual kit, a rear fit problem can start at the front support. Keep the original transmission bracket and its hardware with the parts you plan to reuse.
This guide separates the front bracket, center hanger and driver-side rear support. Check each in order instead of trying to level the tailpipes by moving the tips alone.
U.S. emissions rules prohibit tampering with certified controls. A race-use label alone does not establish an exemption.
Identify The Late-LML Front Connection And Dual Route
Tip — Rear-route restriction: The matching Flo-Pro LML dual reference calls for removing the factory spare tire and its shield and excludes under-bed gooseneck hitches. Check the exact route before teardown. This does not establish the same restriction for every LML kit or permit removal of unrelated heat shielding.
| Vehicle or layout check | What applies here |
|---|---|
| Truck covered | 2015.5–2016 Chevrolet/GMC 6.6L LML Duramax. |
| Front connection | Illustrated three-bolt turbo-direct/front-pipe connection; check transition-year hardware on the truck. |
| Original front support | Retain the transmission-mounted bracket and its hardware. |
| Rear route | 5-inch downpipe-back dual exit; added driver-side bracket uses its third hole. |
| Scope | Exhaust fitting. Other underhood or control-system work needs separate instructions. |
Before You Remove Anything: This guide covers the 2015.5–2016 6.6L LML with the illustrated three-bolt turbo-direct/front-pipe connection and a 5-inch dual rear route. Confirm the connection on the truck rather than relying on the calendar year alone. Earlier-style front hardware and a retained-DPF rear system use different procedures.
Late-LML Pipe List And Bracket Locations
| Component name | Illustrated manual reference | How to identify or fit it |
|---|---|---|
| Three-bolt front/downpipe section | 11511 in the steps and matching Flo-Pro reference; 11211 in the packing artwork | Treat this as one front section. Match the three-bolt flange, bend and hanger; the packing label conflicts. |
| Intermediate pipe | 11252 | Its hanger and support clamp locate the center route. |
| Intermediate hanger clamp | CH54 | Seat in the corresponding stock rubber support. |
| Center extensions | 50012 / 50018 | Measure after setting the splitter and rear branches. |
| Y-pipe | Y500 | Feeds the two over-axle branches. |
| Driver-side over-axle pipe / tailpipe | 11360 / 11361 | Uses the added driver-side support. |
| Passenger-side over-axle pipe / tailpipe | 11358 / 11359 | Uses the passenger-side factory support. |
| Added driver-side hanger | H1 | The illustrated bracket uses its third hole. |
Use the shapes, pipe ends and welded supports in this drawing to match the components listed above.
Tools For The Front Flange And Transmission Bracket
| Tool Or Equipment | What You Need It For |
|---|---|
| Front flange | 15 mm socket, listed in ES08678S5.0. Retain the original nuts. |
| Transmission hanger bracket | 13 mm socket or wrench, listed in ES08678S5.0. |
| Extensions and rear route | Stands, tape measure and cutting tools if needed; torque wrench with hardware-specific values. |
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: Remove The Stock Sections And Retain The Front Support
Installer Tip: Check the retained front bracket and its upper rubber hole before building the rear route. Keep the front pipe adjustable while the bracket is refitted.
Step 1: Release The Stock Exhaust
With the stock assembly supported, label the electrical and pressure-line connections and release them at the proper connectors. Open the downstream four-bolt flange and free the rubber hangers. Do not confuse that downstream connection with the three-bolt front joint used by this late-LML route.
Step 2: Keep The Front Nuts And Support Bracket
The illustrated three-bolt front joint uses a 15 mm socket; save the original nuts. Remove the transmission-mounted hanger bracket with a 13 mm tool to release the front pipe. Keep the bracket and its hardware. Support the pipe so its weight cannot lever against the turbo-direct connection.
Phase 2: Rebuild The Front And Center Supports
Step 3: Fit The Front Pipe And Restore Its Support
Match the single front pipe by its three-bolt flange, bend and welded hanger. Put its rod through the upper hole of the original rubber isolator. Start the front flange loosely, then bolt the saved bracket back onto the transmission before measuring the center. The number-table note handles the conflicting packing label.
Step 4: Add The Intermediate Pipe And Hanger Clamp
Connect the intermediate pipe behind the front section and seat its factory support. Fit the intermediate hanger clamp into its corresponding rubber mount before adding the extensions. Leave its clamp loose so the pipe can turn during rear alignment.
Step 5: Set The Wheelbase Extensions
Trial-fit the center extensions without cutting. Hang the Y-pipe and rear branches before setting final length. Measure the supported gap and actual insertion at each joint. The approximate 5-inch connection allowance is not a separate addition at every pipe end. Cut only the allowed plain end, then deburr and trial-fit again.
Phase 3: Add The Third-Hole Driver Support And Both Exits
Step 6: Fit The Third-Hole Driver Support And Rear Branch
Mount the added driver-side bracket through the existing frame hole behind the upper shock mount. This illustrated LML bracket uses its third hole, with metal inside the frame and rubber outward. Add the Y-pipe, driver over-axle pipe and driver tailpipe. Keep their joints adjustable.
Step 7: Build The Passenger Side
Fit the passenger over-axle pipe to the matching splitter outlet, then add its tailpipe. Seat the stock rubber mounts before setting height. Keep the left and right pipe pairs on their intended sides; their bends and hanger positions differ.
Step 8: Check Both Exits Together
Stand behind the truck and compare the two outlets. Check the brake lines, parking-brake cables and axle vent. Fix the pipe position before tightening anything against a line or cable.
If the Left Outlet Is Low, Check the Support Before Cutting
Confirm the third-hole bracket setting and the rubber facing outward. Recheck the restored transmission support and center hanger. A support-height error is not fixed by shortening a center extension.
With both branches seated, finish the center measurement. For one two-ended slip section, include the end-face gap and each actual insertion once. Rotate the loose rear joints to level the outlets before the final tightening pass.
Step 9: Tighten From The Front
With both branches supported and aligned, tighten the front flange and work rearward. Recheck added driver-side support and the outlet heights as you go. Use the proper specs for the actual clamps and bolts.
Final Check: Front Bracket, Center Hanger And Rear Support Agree
- Front support: The transmission bracket is restored, with the front rod in the upper rubber hole.
- Intermediate support: The hanger clamp is seated before the center length is finalized.
- Driver rear support: The illustrated added bracket uses its third hole, with metal inside the frame and rubber outward.
- Rear branches: Both side-specific pairs are seated, outlets compared and nearby lines clear 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.
Troubleshoot The Bracket And Driver-Side Height
| What you find | What to check before changing parts |
|---|---|
| Front flange does not sit flat | Check late-LML three-bolt hardware and gasket seating. Do not use the nuts to force mismatched faces together. |
| Center pipe hangs low | Refit the transmission bracket and intermediate support before changing extension length. |
| Left outlet is lower than the right | Check the added bracket’s hole and orientation, then rotate the loose rear branch. |
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
Keep the transmission bracket, seat the front hanger in its upper rubber hole, and install added driver-side support at the LML position shown above. Compare both outlets with both sides supported. The all-in-one package also contains work beyond this exhaust procedure.
For the illustrated SPEtuner package, browse LML Duramax parts and compare the 2015.5–2016 5-inch dual option. The all-in-one package also contains other equipment; this article covers the exhaust route only.
Find The Late-LML Dual Package
Look for the 2015.5–2016 dual-exhaust all-in-one option, SKU #11221. It includes more than exhaust hardware. Follow separate instructions for EGR work and tuner setup.
References
Flo-Pro three-bolt LML dual-system reference — Cross-check the applicable support and routing notes; do not transfer another system’s cut lengths or hardware settings.
- SPEtuner: "ES08678S5.0 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: "Bull-Doser: "'16 Chevrolet Silverado 2500HD LTZ Crew Cab (MIAS '16).jpg — Public domain. Layout added; vehicle photo retained." Available from Cover photo: Bull-Doser.
FAQ
Q: What Makes The Late-LML Dual Install Different From The L5P One?
A: This late-LML route uses the illustrated three-bolt front connection, the upper rubber hole at the transmission bracket and the added driver-side bracket’s third hole. Do not copy the L5P support setting.
Q: Why Will The Front Pipe Not Seat Correctly?
A: Check the late-LML three-bolt connection, mating faces and front hanger position. The packing label conflict does not mean two front pipes must be fitted in sequence.
Q: Which Hole Does The Added LML Rear Support Use?
A: The illustrated LML added bracket uses its third hole. Check the bracket orientation and frame location before setting outlet height.
Q: Where Does The Front Hanger Sit In The Rubber Mount?
A: The guide shows the upper hole in the transmission-mounted bracket’s rubber insulator.
Q: Do I Reuse The Original Turbo-Direct-Pipe Nuts?
A: Yes. The PDF tells you to keep them for the new front connection. Check their condition before reuse.
Q: When Should I Fit The Intermediate Hanger Clamp?
A: Fit it with the intermediate pipe in the matching stock support before adding extensions. Keep the clamp adjustable until the complete route is aligned.
Lars
Diesel Performance Engineer | 15+ Years Experience
"Empower Your Beast: Run Cooler, Pull Harder, Last Longer."
