GrudgeBox Builder's Kit

Built to take high horsepower abuse found in late model H-D performance applications while providing elegant shift precision.

Transmission Configurations

GrudgeBox - Straight 1st, 2nd 3rd, 4th, 5th and 6th gears, design and geared for performance buffs, racers and speed freaks seeking negligible power loss.

• All gears are straight cut for negligible parasitic power loss, providing maximum power transfer to the rear wheel
• Wide ratio gearing for heavier performance applications
• Built for aggressive takes offs and long distances at above average speeds
• 250 RPM drop at higher highway speeds (approx. 80 mph)
• Engineering focus on excessive durability
• Bulletproof main drive gear bearing (patent pending)
• Gears up to 40% wider than stock
• Positive dog tooth engagement in gear with pie shaped shift dogs
• Frictionless linear detent shift system for smooth shifting
• Redundant neutral detent to make it easy to find neutral
• Low effort, single axis/linear motion ratchet pawl for crisp, tight and easy shifting
• More durable than stock
• No case modifications required for installation

Thightly-tuned

4° Back Cut Shift Dogs

More hook for the hold! The 4° back cut angle on all GrudgeBox shift dogs ensures positive gear engagement and eliminates hop out.

Shift System

Shift with certainty! The GrudgeBox features our frictionless linear detent shift system. The shift drum utilizes a fixed spindle design for smooth, low inertia, indexing. It’s easy to find neutral with our redundant neutral detent, which is incorporated into the architecture of the shift system.

1. Smooth linear 11/32” detent ball bearing riding on 60 micro ball bearings
2. Linear motion is controlled by a caged 24 micro ball bearing assembly
3. 44lb/in compression spring

New Pawl Design 

Shift with ease! Conventional shifter pawls have a 2-point pivot system. Our new low effort single axis/linear motion shifter pawl rotates from one central pivot point, allowing continuous motion throughout the shift. Overshift inhibitors prevent any missed shifts.

Speedometer Reluctor Ring

Stay calibrated! The GrudgeBox utilizes a speedometer reluctor ring for sending the vehicle speed signal through the stock speed sensor, keeping the pulses per mile the same as stock. Your speedometer will indicate the correct speed without the use of a recalibration box. PCM reflash is required for correct gear indication and proper cruise control operation.

Bigger Gears

Stronger! The GrudgeBox gears are up to 40% wider than stock for superior strength and durability.

Pie Shaped Shift Dogs

Positive shift engagement! Intended for high horsepower applications and well suited for everyday cruising, the pie shaped shift dogs used in the GrudgeBox provide significantly more dog tooth/pocket landing area for positive dog tooth engagement while in gear.

Main Drive Gear Bearing 

Bulletproof! The GrudgeBox comes with our exclusive double tapered roller bearing assembly (patent pending) to eliminate the all too common stock main drive gear bearing failures.

Simpler Pawl Design 

Built for a beating! Conventional shifter pawls have a 2-point pivot system. Our new single axis/linear motion shifter pawl has fewer points of motion and will hold up under high horsepower and aggressive shifting.