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GrudgeBox Builder's Kit

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!



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
  • No case modifications are required for installation 
  • 2006-Later Dyna
  • 2007-Later Softail & Touring*

*Does not fit 2023 and later CVO models.


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














New PN

Old PN





GrudgeBox, 3.15 1st gear ratio

2006-Later Dyna, 2007-Later Softail/Touring



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.


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

Learn more about Spectro Performance Oils here:

Click here for the GrudgeBox Instructions GrudgeBox Instructions


BAKER Drivetrain reserves the right to change prices, terms or policies at any time without notice. Orders can be pre-paid using Visa, MasterCard, American Express, Discover or PayPal. All orders not pre-paid will be sent C.O.D. certified check or money order only unless pre-approved for company check acceptance. Any orders from outside the USA must be pre-paid in US funds via wire transfer; a $30 transfer fee will apply. Prices shown are F.O.B. Haslett, MI.


BAKER™ transmission assemblies and transmission builder 's kits, are guaranteed to the original purchaser to be free of manufacturing defects in materials and workmanship for a period of 5 years from the date of purchase or up to 50,000 miles, whichever occurs first. All other BAKER products are guaranteed to the original purchaser to be free of manufacturing defects in materials and workmanship for a period of 2 years from the date of purchase or up to 24,000 miles, whichever occurs first, except for the following; Warranty does not cover clutch plate wear, throw out bearing failures or mainshaft breakage due to improper clutch nut installation.Electrical components carry a 30-day warranty; cosmetic finishes (chrome plating, hard anodizing, powder coating) are covered for 60 days. Certain promotional products may carry a shorter warranty as specified at the time of purchase. If the product is found by BAKER to be defective, such products will, at the option of BAKER, be replaced or repaired at cost to BAKER.In the event warranty service is required, the original purchaser must call or write BAKER immediately with a description of the problem. If it is deemed necessary for BAKER to make an evaluation to determine whether the transmission assembly or transmission kit or accessory is defective, the entire transmission assembly, whether originally purchased as an assembly or kit, must be properly packaged and returned prepaid to BAKER with a copy of the original purchase invoice. If after evaluation by BAKER a defect in materials and/or workmanship is found, BAKER will, at their option, repair or replace the defective part of the assembly.


Returns are permitted within 90 days of the delivery date. Any merchandise returned for any reason (exchange, credit or modification) must be accompanied by a Return Goods Authorization (RGA) number or it will be refused. Call BAKER to obtain this number prior to returning goods for any reason. There is a 15% re-stocking fee for all returned items. BAKER is not liable for any shipping.


NOTE: Limited warranty does not cover labor or other costs or expenses incidental to the repair and or replacement of BAKER products.This warranty does not apply if one or more of the following situations is judged by BAKER to be relevant: BAKER OEM transmissions ; (these are subject to the OEM manufacturers warranty only), Improper installation , accident, modification (including but not limited to use of unauthorized parts, transmission oils or lubricants), racing, high performance application, mishandling, misapplication, neglect (including but not limited to improper maintenance), or improper repair.BAKER shall not be liable for any consequential or incidental damages arising out of or in connection with a BAKER transmission assembly, transmission kit, component or part. Consequential damages shall include without limitation, loss of use, income or profit, or losses sustained as the result of injury (including death) to any person or loss of or damage to property.BAKER transmissions, transmission kits and accessories are designed exclusively for use in American V-Twin motorcycles. BAKER shall have no warranty or liability obligation if BAKER parts are used in any other application.If it is determined that a BAKER product has been disassembled during the warranty period for any reason, this limited warranty will no longer apply unless you were instructed to do so by a BAKER Drivetrain technician for diagnostic purposes.

GrudgeBox Builder's Kit
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Customer Reviews
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United States United States
  • What model motorcycle do you ride? 07 FLHPI Roadking

Awesome Transmission, just get one !!

Would definitely recommend, I know it's pricey but well worth the money as far as I'm concerned........never miss a gear pops into neutral like butter. It's a noisy transmission but I like hearing it do it's thang. Have about 10k miles on it no trouble.

Mark D.
United States United States
  • What model motorcycle do you ride? CVO Road Glide


This transmission moves this bike as if the bike was non existent. Its awesome and I can definitely feel the increased power vs the stock. I still have this "neutral rattle" thing going on but Baker is working with me on it.

Dalibor D.
Australia Australia

All round perfect

Would definitely recommend to anyone. Awesome product and perfect customer service.

United States United States
  • What model motorcycle do you ride? 2022 street glide st

The best Sales and support

Fantastic could not have been any better hard to say more.

BAKER Drivetrain GrudgeBox Builder's Kit Review
Corinna T.
United States United States
  • What model motorcycle do you ride? 2022 FLHTCUTG


purchased for a customer who travels ALOT and he LOVES this kit!

Web Product ID: 5546426819
Baker Drivetrain Team Illustration