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Montana Exhaust & Muffler Laws (2026)
Info: Your vehicle needs a muffler in good working order that prevents excessive noise and smoke.
InfoVerified Jun 19, 2026
Your vehicle needs a muffler in good working order that prevents excessive noise and smoke. Muffler cutouts and bypasses (which route exhaust around the muffler) are prohibited. Montana sets no fixed decibel limit (Mont. Code Ann. § 61-9-403).
Official source: mca.legmt.gov →
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