6 into 4 Signature Series


An all new look to one of our most popular transmissions.  The 6-into-4 Signature Series is an aesthetically lifted Limited Edition version of the 6-into-4.  With an all new case that wraps the gearset and internals as tight as possible. Boasting a true Function Formed Design with an even more nostalgic look. We achieved this by adding the vintage looking ribs, reminiscent of a 60’s era 8-71 blower.   In spirit of the series we added the bronze case badge for that true old school look.



– 6061-T6 3-D Machined billet case with the nostalgic look of 60’s era 8-71 blower and 4 speed had a love child. Precision machined for no leaks and modern day 6 speed performance.

– Bronze Case ID badge.

– 5th mounting stud machined into the case, for pure strength and no weak points

– BAKER Klassic Kicker gears, stainless steel kick arm, and bronze pedal standard

– Case only available with primary flange; raw, or polished

– 23 tooth sprocket standard. Optional 24 tooth and 33 tooth pulley

– Signature Series Ribbed, Forged top cover available with or without neutral switch. Only available on 6N4 Signature Series Transmission. Only available in polished finish.

– Standard with Cast Replica Kicker cover, available in polished or raw finish.

– Modern 5-speed style shift drum and shifter pawl for smooth quick shifts

– Electronic speed sensor provision on left rear of case

– N1 drum, no cost option, for N-1-2-3-4-5-6 shift pattern

– Comes standard with a BAKER 5 Year/50,000 mile warranty

– Available with 36-64, 65-69, 70-E84, 84-86 & modern style splined mainshaft.

– BAKER outboard bearing support compatible.

– Limited Production Run





– 1936-1986 FL™/FX™ Shovelhead™, Panhead™,
Knucklehead™, Sturgis Shovelhead™

– Custom Applications



Case Options & Provisions

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 1970-1986 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.    Depending on what type of electronic speedometer you use, an additional speedometer recalibration box might have to be purchased, BAKER PN 95E-56A.

Machined 5th Stud vs. Bolted on 5th Stud

No Ear and Ear Cases

Electronic Speedo Provision, shown with H-D PN 74437-96 Speedo sensor

Recalibration Box  95E-56A


6-into-4 mainshafts

 Mainshaft Options

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

-1970-Early 1984 length mainshaft.  Shovelhead 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)

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


Klassic Kicker Gears

Kicker Gears

The Signature Series 6-into-4 comes standard with our Klassic Kicker Gears standard. 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, charges might 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 or you can upgrade to the Voyeur top cover that shows the internal beauty of the 6-into-4.


Gear Ratio Options

Gear Ratios
1st Gear 2.94, 2.82 R-Ratio
2nd Gear 2.21, 2.08 R-Ratio
3rd Gear 1.60
4th Gear 1.23
5th Gear 1.00
6th Gear 0.86, 0.80 Deep Overdrive


PN Description Fitment
6402 Close ratio 2.94 1st gear (Standard) 1936-86 FL & FX; good all around gear ratio
6412 3.24 1st gear 1936-86 FL & FX; for heavy GVW applications
64212 R-Ratio 2.82 1st & 2.08 2nd 1936-86 FL & FX; for light hot rods



Deep overdrive 6th gear (0.80) available as no-cost option, consult BAKER tech line

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:

Case finishes: R=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: Standard chrome kicker cover shown in image on page 9. Optional kicker cover suffixes:

FF= function formed polished, BPH=Billet polished Hydraulic, BPM=billet polished mechanical,

BC=billet cable type, E=electric start

Mainshaft length: 1970-E84 mainshaft standard, optional lengths: -36 for 1936-64 mainshaft,-65 for 1965-69 mainshaft, -84 for 1984-86

23 Tooth sprocket standard. Specify optional 24 Tooth sprocket by adding -24 suffix or -33 for pulley

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)



1976 Shovelhead, M6402R 6-into-4 Raw, Cycle Shack Exhaust

– 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.

– 6-into-4 case does not have speedometer cable provision on front of case

– 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 link below to check out some aftermarket exhausts that will fit your 6-into-4.

-Cycle Shack

-Kleiv Motorcycle Products


Recommended upgrades


– 6-into-4 Outer Bearing support, used when not running a inner primary plate

– The TTP, ‘Tin Type Primary’

– Straight Kicker Arm; standard length or +1 inch

-33-Tooth Trans pulley for belt drive final

Click on any of the images below to learn more

6-into-4 Outer Bearing Support

Tin Type Primary

+1 Straight Kicker and Pedal

33 Tooth Pulley



Spectro Oil BD-75140

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 Click Here


1st Gear Design Change
1st Gear Change Addendum-March 2012: Click Here

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6-into-4 Signature Series, front right, macro

6-into-4 Signature Series, front right,

6-into-4 Signature Series, front right

6-into-4 Signature Series, close up of emblem

6-into-4 Signature Series, rear right

6-into-4 Signature Series, rear right

M6402R, 6-into-4 70-84 mainshaft, 2.94 1st gear .86 6th gear

H6402P-FF, 6-into-4, polished, 70-84 mainshaft, Function Formed Hydraulic Kicker, 2.94 1st gear .86 6th gear

M402P, 6-into-4 ready for assembly

E6402R-84, 6-into-4, raw case, late 84 shaft, electric start no kicker, 33 tooth belt pulley

E6402R-84, 6-into-4, raw case, late 84 shaft, electric start no kicker, 33 tooth belt pulley

M6402B, 6-into-4, wrinkle black, standard mechanical kicker, 23 tooth sprocket



1978 Shovelhead, M6402R 6-into-4, Kleiv Exhaust

1978 Shovelhead, M6402R 6-into-4, Kleiv Exhaust

Kevin from Cycle Works Shovelhead, E6402R 6-into-4, Cycle Shack exhaust


Serge McCabe’s 1981 Shovel, M6402R 6-into-4, Kleiv exhaust w/baffles

Serge McCabe’s 1981 Shovel, M6402R 6-into-4, Kleiv exhaust w/baffles

Jay Allen’s Army Tribute Rolling Thunder Bike

Featured in the cult motorcycle movie Choppertown: the Sinners. Check out the Choppertown DVD here Or check out Choppertown on YouTube Here.



BAKER DRIVETRAIN| 9804 E. SAGINAW, HASLETT, MI, 48840 |1-877-640-2004| 517-339-3835 | FAX: 517-339-4590 @2012 BAKER INC