Share to FB

6-into-4 "Signature Series" Complete Transmission

This is the highest form of the famous BAKER 6-into-4. With a Function-Formed top cover and case, we thought is was worthy of it's own product page with it's own photos. 

As a 6-into-4, this gem is made to satisfy the old school tendencies while providing the ability to run reasonable RPM’s at highway look extremely customized. Panhead and Shovelhead riders will love the ability to ride hard with their friends on late model bikes.


  • OD6-based transmission inside
  • Many gear ratio options
  • Many case, bearing door, shift system and cover options


  • Smooth out the rattle on the highway
  • Stay in the powerband

    Case: The 6-Into-4 Transmission case comes in two different versions. Our 1936-64 case has no ear,  to work with the factory primary. Our 1965-1986 version includes  the primary ear bosses. These can be used with stock primary applications, belt drive applications, or running no primary plate at all.

    4 different mainshafts available for Knucklehead, Panhead or Shovelhead:

    • 1936 to 1964 Tapered Mainshaft

    • 1965 to 1969 Tapered Mainshaft

    • 1970 to E1984 Tapered Mainshaft 

    • 1970 to E1984 Splined Mainshaft

    1st Gear Ratio: The 2.94 1st gear ratio fits 1936-1986 FL & FX models. This gear ratio is an all around good ratio. The optional 3.24 1st gear ratio fits 1936-1986 FL & FX models and is recommended for heavy GVW applications. The R-Ratio 2.82 1st gear is for 1936-1986 FL & FX models and is recommended for light hot rods.

    2nd Gear Ratio: We recommend a 2.21 2nd gear ratio for the 2.94 and 3.24 1st gear ratios. The 2.08 2nd gear is normally paired with the 2.82 1st gear for racing applications. If you would like a personalized 2nd gear pairing, please contact us through the website chat, email us at, or call us Monday-Friday 8AM-7PM EST/EDT and Saturday 10AM-3PM EST/EDT at 517-339-3835.

    All 6-into-4 case options come with a machined in 5th stud. We took the weakest point on other aftermarket transmissions and made it into the strongest point on ours. The 5th stud commonly breaks out of its bolted on plate causing your driveline to tweak in the chassis. The 6-Into-4 Transmission case comes in two different versions. Our 1936-64 case is a no ear case to work with the factory primary. Our 1965-1986 version comes with the primary ear bosses on it. These can be used with stock primary applications, belt drive applications, or running no primary plate at all. We do recommend the use of our bearing support for this application, BAKER PN 6-4SSP-A. Both cases have a provision for an electronic speedometer.The electronic speedometer would utilize a stock 1996-2006 speed sensor, PN 74437-96.Pending what type of electronic speedometer you use, an additional speedometer recalibration box might have to be purchased, BAKER PN 95E-56B. The BAKER 6-into-4 case does not have a gear drive speedometer cable provision on the case. 

    • Late 1984-1986 length mainshaft.  Diaphragm type wet clutch.

    • 1970-Early 1984 length mainshaft.  Shovelhead mainshaft.

    • 1970-Early 1984 Splined mainshaft. Shovelhead splined mainshaft.

    • 1965-1969 length mainshaft.  Panhead/Shovelhead.

    • 1936-1964 length mainshaft.  Knuckle/Panhead mainshaft.    

    Shift Drum Options

    • Standard Drum Shift Pattern (1-N-2-3-4-5-6 shift pattern)

    • Revesre Drum Shift Pattern (6-5-4-3-2-N-1 shift pattern)

    • N1 Drum Shift Pattern (N-1-2-3-4-5-6 shift pattern)

    Klassic Kicker Gears

    Kicker Gears All BAKER 4-Speeds come standard with our Klassic Kicker Gears. Made out of 1018 HR Steel, tumble finished to around a 20 micro and heat treated to 50-55 RC; these gears roll smooth as glass. 

    Kicker Cover Options

    We manufacture and offer 6 different kicker covers making the 6-into-4 completely customizable from stock to custom build. Our kicker covers come in different finishes ranging from the standard chrome cover to the raw replica cover to the show polished Function Form Hydraulic cover.  To see the full line of kicker covers available Click Here.  Depending on the choice of cover and finish, additional charges may apply.  

    Top Cover Options

    The 6-into-4 comes standard with a single pole neutral switch top cover with our hidden vent.  The transmission can be ordered with our no-neutral top cover.

    Gear Ratios

    The 6-into-4 comes in a standard, optional or R-Ratio configuration



    1st Gear

    2.94 / Optional 3.24

    2nd Gear


    3rd Gear


    4th Gear


    5th Gear


    6th Gear




    1st Gear


    2nd Gear


    3rd Gear


    4th Gear


    5th Gear


    6th Gear







    2.94 1st gear (Standard)

    1936-86 FL & FX; good all around gear ratio


    3.24 1st gear

    1936-86 FL & FX; for heavy GVW applications


    R-Ratio 2.82 1st & 2.08 2nd

    1936-86 FL & FX; for light hot rods


    Each transmission is hand built to order. Use the base part number above and add suffixes (with a “-“ before each suffix) to specify the desired configuration:

    Signature Series: Add a ‘S’ suffix for a polished signature series trans, or ‘RS’ for raw finished case. (DOES NOT INCLUDE NO EAR 6-INTO-4’S) Click Here for Signature Series Page Case

    FinishesR=raw/casted, B=wrinkle black, P=polished

    Drum Option: N1=N1 drum (N-1-2-3-4-5-6 shift pattern)

    Case Style: Standard case has ‘4-stud ears‘ for primary, specify no ear case by adding NE suffix (1936 style)

    Kicker Cover: Chrome Die Cast Clutch Arm Kicker Cover Standard. Optional kicker cover suffixes:

    • FF= function formed polished

    • BPH=Billet polished Hydraulic

    • BPM=billet polished mechanical

    • BC=billet cable type

    • E=electric start

    Mainshaft: 1970-E84 mainshaft standard, Optional lengths:

    • 36 for 1936-64 mainshaft

    • 65 for 1965-69 mainshaft

    • 84 for 1984-86

    Sprocket: 23 Tooth Chain sprocket standard. Specify optional 24 Tooth Chain sprocket by adding -24 suffix or -33 for Belt Pulley – 6-into-4 has 2 more gears than a 4-speed and sticks out 1.6” more. Rear exhaust pipe, oil tank brackets, and starter brackets may have to be modified for fitment. – Electric speed sensor provision in case accepts stock 1994-up speed sensors. – Some 1970s inner primaries may require modification for sprocket nut clearance.

    Recommended Exhausts 

    With the factory exhaust not fitting in most cases, two different exhaust companies took charge.  Click on either of the links below to check out some aftermarket exhausts that will fit your 6-into-4.1976 Shovelhead, M6402R 6-into-4 Raw, Cycle Shack* Exhaust shown.

    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 6-into-4 Fluid Capacity Dry: 22-24fl-oz BAKER 6-into-4 Fluid Capacity Wet: 18-22fl-oz  



     BAKER 6-into-4 install instructions with exploded views
    1st Gear Design Change 1st Gear Change Addendum-March 2012 




    Standard Gear Case Finish Examples (Not applicable to all products)




    Wrinkle Black

    These example finishes are intended to show the exterior treatments of cases, top covers and doors.

    TERM AND CONDITIONS                                                                                         


    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, transmission kits, primaries, and oil pans 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. BAKER™ clutches, kicker cover kits, belt drives, F6F kit, reverse systems, covers and accessories 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. 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 invoice of purchase. If after an evaluation has been made by BAKER™ and a defect in materials and/or workmanship is found, BAKER™  will, at BAKER™  option, repair or replace the defective part of the assembly. 




    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 charges. 




    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 manufactures 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.


    The words H-D®, Softail®, FXR®, Dyna®, FLT®, FLH®, Sportster®, and Buell® are registered trademarks and are for reference only.


    Customer Reviews

    Based on 1 review Write a review
    Questions? Ask us anything:
    Contact us
    Or just call us at 517-339-3835. We're glad to help.

    6-into-4 "Signature Series" Complete Transmission
    Move your mouse over image to zoom. Click to enlarge.
    6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission 6-into-4 "Signature Series" Complete Transmission