Product Description
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.
Fitment
- 2006-later Dyna
- 2007-later Softail & Touring
FEATURES
- 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 take-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
GrudgeBox Installation Instructions for 3.15 1st gear
TIGHTLY-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.- A) Smooth linear 11/32” detent ball bearing riding on 60 micro ball bearings
- B) Linear motion is controlled by a caged 24 micro ball bearing assembly
- C) 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. - DynoJet Power Vision calibration numbers:
- 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.
OVERDRIVEN
- New Generation OVERDRIVE
Cruise at 80 mph with the overdrive 6th gear, lowering RPM on the highway for improved fuel economy, reduced vibration and less wear and tear on the rider. - .92 overdrive in 6th gear provides a 250 rpm reduction while cruising at 80 mph.
Transmission Ratios
GrudgeBox |
Stock H-D |
1st–3.15 |
1st–3.34 |
2nd–2.21 |
2nd–2.31 |
3rd–1.59 |
3rd–1.72 |
4th–1.23 |
4th–1.39 |
5th–1.00 |
5th–1.19 |
6th–0.92 |
6th–1.00 |
NEW PN |
Old PN |
Description |
Fitment |
GB6- |
GBSTR |
GrudgeBox, 3.15 1st gear ratio |
2006-Later Dyna, 2007-Later Softail/Touring |
GB6-M8 | GBSTR17 | GrudgeBox, 3.15 1st gear ratio | 2017 Milwaukee 8 models |
Engineered and manufactured in the USA with a focus on excessive torque capacity and crisp shifting. Included is our 5-year/50,000 mile limited warranty for worry-free, aggressive riding.