BAKER 6 into 4 Transmissions

When Harley-Davidson first introduced four-speed transmissions, it was a technical breakthrough. Even though some people question the value of having more gears — “the engine already has enough torque!” — the fact remains that more closely spaced gears allow a combustion engine to operate more consistently within its optimal RPM range than fewer gears with wide ratio-steps. That’s why BAKER has packed not just five, but six gears into a case that fits the old four-speed frames. Riders who gave it a try confirm that performance and acceleration are significantly smoother and stronger with the additional two gears.

Gears one through four are closely spaced, the fifth gear is a direct drive (equivalent to the fourth gear in a four-speed transmission), and with a ratio of 0.86, the sixth gear reduces RPMs by another 500 compared to fifth.

On the left side, the primary cover corresponding to the model year fits (tin or aluminum), while a kicker is flanged on the right side. Not all primary covers, however, are compatible with the five-speed pinion used — please check.

Because the transmission is wider on the right than the old four-speed unit, the original exhaust may get in the way. You need to consider this when planning the conversion, as well as that the shift mechanism and cover are taken from Harley’s five-speed gearboxes. Thus depending on your setup, the oil tank and battery tray may also require modifications.

There is no provision for mechanical speedo drive, but the case accepts a sensor. The sensor-triggering gear has 37 teeth.

Gear ratios:

• 1st - 2.94:1
• 2nd - 2.21:1
• 3rd - 1.60:1
• 4th - 1:1.23
• 5th - 1:1
• 6th - 1:0.86