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Baker Drivetrain GrudgeBox - Black Door - M8 Touring Models 2017 later

Original price $3,695.00 - Original price $3,695.00
Original price
$3,695.00 - $3,695.00
Current price $3,695.00

Baker GrudgeBox, Black Door, 

The GrudgeBox is a tough overdrive 6-speed to replace your stock 6-speed!

The GrudgeBox was engineered with a focus on excessive torque capacity and crisp shifting. All gears are straight cut in a way that ensures maximum power transfer to the rear wheel. This gearset was designed and geared for the everyday highway riders, speed freaks, and even racers!

Fits:  2017-Up M8 Touring, Black Door, Standard Shift Pattern

*Does not fit 2023 and later CVO models.

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

  • 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
  • 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
  • Typically no clearance is required- the gearset is designed to fit in an OEM case. On occasion, the case may require clearance due to OEM fluctuations in the case casting process. 

The GrudgeBox has different gear ratios than the stock transmission (except GrudgeBox 5th gear is the same as stock 6th gear, 1:1). This changes the input to the ECM. The 42-tooth reluctor ring in the GrudgeBox compensates to correct the speedometer within ± 2 mph with no re-flash to the ECM. However, the gear indicator and cruise control may only operate in 5th gear. To correct the gear indicator in all gears and enable cruise control in 3rd, 4th, and 6th, an ECM re-flash is required. Existing tuners must have an option to modify transmission gear ratios in order to re-flash the ECM.  BAKER Drivetrain offers re-flash values for Powervision, ThunderMax, TTS, and Techno Research tuners. 

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.


  • 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.


  • 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.
  • 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.


  • 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 


Stock H-D














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.

Recommended Fluid Level

Picking the right transmission fluid ensures the life and durability of your transmission, that’s why BAKER recommends a fully synthetic GL-5 rated gear weight oil of 75W-140. If a GL-5 rated gear lube is not available, these commonly carried viscosities (weights) will work 75W-90, 75W-140 and 85W-140. BAKER does not recommend the use of Syn3 (20W-50). For Bert’s article on ‘Oil & Spiders’ Click Here

  • BAKER GrudgeBox Fluid Capacity Dry: 28-32fl-oz
  • BAKER GrudgeBox Fluid Capacity Wet: 24-28fl-oz