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

CONTROL YOUR EXHAUST SOUND

  • OPEN MODE

    Flip the switch. Valve opens. Full open-pipe sound and unrestricted flow. For when you want to be heard.

  • CLOSED MODE

    The same muffler becomes a quiet exhaust muffler for early mornings and residential streets.

  • BUILT TO LAST

    304 stainless, TIG-welded, electronic actuator with a 5A fused harness. Built to outlast the truck.

CHOOSE YOUR VARIABLE MUFFLER

Two sizes. Same build standard.

  • HMD 4" Variable Muffler, three-quarter angle view
1 6

HMD Fabrications

4" Variable Muffler

$499.99 USD
$499.99 USD
Sale Sold out
Shipping calculated at checkout.
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  • HMD 5" Variable Muffler, three-quarter angle view
1 6

HMD Fabrications LLC

5” Variable Muffler

$699.00 USD
$699.00 USD
Sale Sold out
Shipping calculated at checkout.
View full details
SMOG_TRUCK

INSTALLS IN UNDER 30MIN

Cut your existing exhaust to length, clamp the switchable exhaust muffler in, run the wire harness to the included toggle switch. Step‑by‑step guide and install video included with every order.

VARIABLE MUFFLER INSTALL

THE FEEDBACK

What real people are saying.

DM
@durrrrtymax

Freaking awesome dudes! Wow! A much needed solution that will carve its way as a new standard in the space!

ME
@marquez.ervin

I got faith this will go somewhere keep up the work 🔥

IF
@isaiahfraustoo

Shits boutta sell out so fast😭

MR
@mannyr24

Love to try it on my f350 🔥

GF
@gemcityfireman

This is exactly what the market needed. The "other" brand is pretty pricey. When I get mine it's going to be hooked up to the Aux switch on my Ram. You guys are going to hit a home run with this🫡

GG
@grit.andgears

That is a crazy difference. Nice work!

Tag @hmdfabrications to be featured.

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.