If you are running a high-horsepower late-model Harley, you already know the factory transmission can be the weakest link. The GrudgeBox was built specifically to solve that problem. It is a tough overdrive 6-speed gearset engineered for excessive torque capacity, violent acceleration, and crisp, effortless shifting.
Built to handle straight-up abuse from everyday highway riders, speed freaks, and racers alike, the GrudgeBox delivers:
Maximum Power Transfer: Straight-cut gears up to 40% wider than stock eliminate parasitic power loss, putting every pony directly to the rear wheel.
Effortless, Precision Shifting: Features a frictionless linear detent system, pie-shaped shift dogs, and a low-effort single-axis ratchet pawl for tight, positive engagement.
Hassle-Free Neutral: Built with a redundant neutral detent so you are never stuck searching for neutral at a stoplight.
Cruising Comfort: Wide-ratio gearing gives you aggressive take-offs off the line while knocking down approximately 250 RPM at 80 mph for smooth highway cruising.
EXCLUSIVE: NEW FITMENT COMING SOON
Until now, the GrudgeBox gearset was designed for 2006-later Dynas, 2007-2024 Softails, and 2007-later Touring* (*except 2023-2026 CVO, 2024-2026 Street Glide and 2024-2026 Road Glide) models. But as Harley-Davidson updated its platform, we knew late-model M8 riders needed that same bulletproof reliability.
We’re excited to share the news first: the GrudgeBox Builder’s Kit is coming soon for 2023.5 and later Gen II M8 models with the shift drum actuated gear position sensor.
We have adapted our proven, ultra-durable GrudgeBox platform to fit seamlessly into these newer factory models. You get all the strength, precision shifting, and power handling of the original GrudgeBox, engineered specifically for the latest generation of H-D Touring performance builds.
Keep an eye on your inbox—pre-orders and full release details will be dropping here first before we announce them to the public!
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