6-into-4 Complete Transmission

Made to satisfy the old school tendencies while providing the ability to run reasonable RPM’s at highway speeds. Panhead and Shovelhead riders will love the ability to ride hard with their friends on late model bikes. 

HOW IT'S MADE

See how the 6-into-4 was exemplified as the archetypal motorcycle transmission and used as a focal point for the How It's Made television show on the Discovery Channel.

• 6061-T6 billet bearing door precisely machined and finished in a show polish.
• Forged aluminum top cover made from certified American aluminum, finished off in a high quality show polish.

The sprocket/pulley is not included in the complete transmission assembly. For the acquisition of these components, kindly contact BAKER Drivetrain at 517-339-3835.

• OD6-based transmission inside
• Add “5th” stud integral to the main case housing.

Benefits

• Smooth out the rattle on the highway
• Stay in the powerband
• .86:1 6th gear overdrive for a 14% decrease in cruising RPM at highway speeds
• 2.94 1st gear for an increase in torque off the line

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. For the 1936-1964 Tapered Mainshaft applications, please note that the 6-into-4 case does not contain an alignment track or a provision for the primary adjustment bolt that you would normally find on a stock case. 

4 different mainshafts are available for Knucklehead, Panhead or Shovelhead:

• 1936 to 1964 Tapered Mainshaft**

• 1965 to 1969 Tapered Mainshaft

• 1970 to E1984 Tapered Mainshaft 

• Late 1984 to 1986 Long Tapered Mainshaft 

**For 1936-1964 Tapered Mainshaft applications, please note that the 6-into-4 case does not contain an alignment track or a provision for the primary adjustment bolt that you would normally find on a stock case. 

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. 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.

• 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)

Classic Kicker Gears

Kicker Gears All BAKER 6-into-4s come standard with our Classic 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 3 different kicker covers making the 6-into-4 completely customizable from stock to custom build. Depending on the choice of cover and finish, additional charges may apply.  

The 6-into-4 comes standard with a straight kick arm.

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

Note

Each transmission is hand-built to order.

Clearance: 6-into-4 has 2 more gears than a 4-speed and sticks out 1.6” more. The 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, you will need to make sure that you find an exhaust that goes around the side cover. The 6-into-4 has 2 more gears than a 4-speed and sticks out 1.6” more.

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   

Learn more about Spectro Performance Oils here: https://spectro-oils.com

Instructions

BAKER 6-into-4 install instructions with exploded views