4.9/5.0 Lifetime Weld Warranty Hand-Fabricated, Every Unit Ships in 3-5 Business Days Ships to All of North America Shipped from USA

BEFORE YOU START

  • In the Box

    • 1× Variable muffler (4" or 5" diesel muffler)
    • 2× Stainless band clamps
    • 1× Wiring harness with 5A fuse
    • 1× Toggle switch
    • 1× Installation guide

  • From Your Shop

    • Cutoff wheel or sawzall
    • Welder (optional, clamps work too)
    • 9/16" socket and ratchet
    • Wire stripper and crimps
    • 12V power source (battery or accessory line)
    • Drill (for switch mounting if dash-mounting)

STEP-BY-STEP

  • 01 — Prep your truck

    Park on level ground, set the parking brake, and let the exhaust cool completely. Hot stainless will give you a bad day. If your truck is stock-low, throw it on jack stands for clearance.

  • 02 — Mark and cut your existing exhaust

    Measure your exhaust valve muffler length and mark your cut points on your existing pipe. Use a cutoff wheel or sawzall. Deburr the pipe ends so the clamps seat clean.

  • 03 — Test fit the muffler

    Slide the muffler into position with the band clamps loose. Confirm the inlet and outlet line up with your pipe ends. Check valve orientation — actuator should be accessible, not buried against the chassis. If you're installing the 5 inch muffler, double-check pipe diameter before tightening.

  • 04 — Tighten the clamps

    Once positioned, torque the band clamps to spec. Don't over-tighten — stainless deforms. If you're welding instead of clamping, tack first, check fitment, then run your beads.

  • 05 — Run the wiring harness

    Route the wiring harness from the exhaust valve muffler up to your cab. Avoid heat, moving parts, and sharp edges. Use zip ties to secure every 12 inches.

  • 06 — Mount the toggle switch

    Pick a switch location you can reach without looking — center console, dash blank, or aftermarket switch panel. Drill the mounting hole, install the switch, and connect the harness.

  • 07 — Wire to power

    Connect the harness power lead to a 12V accessory source (switched ignition recommended so the valve doesn't drain when parked). Ground to clean chassis metal. Confirm the inline fuse is seated.

  • 08 — Test it

    Turn the key to accessory or fire it up. Flip the toggle. You should hear and feel the valve click. Run the truck through both modes — you'll get immediate exhaust note control, from quiet cruise to wide‑open rumble. Button everything up once you've confirmed both modes work.

WATCH THE FULL INSTALLATION

TIG-welded seam detail on the HMD 5" Variable Muffler

LIFETIME WELD WARRANTY

If a weld on your exhaust valve muffler fails, we'll fix it or replace it. Period. Damage from accidents, misuse, or abuse isn't covered — but if a seam ever opens up under normal use, you're covered for life.

READ REFUND POLICY
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QUESTIONS? IDEAS? PROBLEMS?

We answer every email ourselves. No support tickets, no AI bots, no outsourced reps. If you've got a question about fitment, want to dial in the perfect exhaust note control with your diesel muffler, or have a problem with your order, we'll get back to you within 24 hours. Email us or send us a DM on Instagram or Facebook.

CONTACT US

FAQs

Valve doesn't click when I flip the switch

Check power first — multimeter the harness leads with the switch in the open position. If you've got 12V at the connector but no movement, the actuator may be seized from shipping. Run the switch back and forth 10-15 times to free it. Still nothing? Email us with your order number.

There's a rattle in closed mode

Usually means the band clamps aren't fully seated. Loosen, reseat the muffler so the clamp grips clean stainless (not heat-tinted weld), and re-torque.

Drone in the cabin even with the valve closed

Drone happens when your exhaust resonates at cruise RPM. Adding a resonator upstream of the muffler kills it without affecting open-mode sound.

Will this void my truck's warranty?

Aftermarket exhaust modifications can affect powertrain warranty coverage. Check with your dealer if you're under warranty. Federal Magnuson-Moss law protects you in some cases — the dealer has to prove the mod caused the failure.

How loud is it open vs closed?

Open mode is roughly the same volume as a straight pipe of equal diameter. Closed mode reduces output by an estimated 8-12 dB at WOT, depending on your full system.

Is it street legal?

Variable mufflers are legal to install in most US states. Operating with the valve open may exceed local sound ordinances depending on where you drive. Ride responsibly.

Does the 5 inch muffler work as a diesel muffler for daily driving?

Absolutely. The 5" model is a direct‑fit diesel muffler for 5‑inch exhaust systems. Closed, it’s a quiet exhaust muffler that tames highway drone. Open, it’s an unrestricted straight pipe—best of both worlds.

How do I get exhaust note control with this setup?

Exhaust note control is built in. Flip the switch to open the valve for full sound, flip it back to close the valve for refined cruising. No extra modules, no tuning.

Will a switchable exhaust pass inspection?

Switchable exhaust systems are legal to install in most states. Operating with the valve open may exceed local sound limits. Always check your local noise ordinances—ride closed in town, open where it’s allowed.