BAKER Torquebox Right Side Drive Heavy Duty Transmission for 1984-1999 Evo Softails

  • Fits 1984-1999 Evo Softail motorcycles.

  • Case sculpted from billet aluminum.

  • Features a show polished finish.

  • Available in 5-Speed or 6-Speed (add $400 for 6-Speed).

  • Backed by a five year / 50,000 mile manufacturer's limited warranty.

  • Two rail shift fork system with common fork used 3 times
  • 2” diameter shift drum suspended by two radial ball bearings mounted to a fixed spindle axis.
  • Ratchet pawl has overshift inhibitor (up and down) and is mounted on two radial ball bearings. shift lever shaft cross sectional area is 65% larger than stock.
  • Frictionless detent system. a 3/8” primary ball bearing is cradled by, and rolls on, 50 secondary micro ball bearings. in turn, the cradle is part of a plunger that actuates during shifting and is guided by a tertiary linear micro ball bearing system.
  • Ignition kill and neutral switches top mounted for easy dwell timing adjustment.
  • Shift system lever ratio is 35% less than stock. bearing mounted shift shaft yields low system hysteresis. short, tight shifts are the result.
  • N-1-2-3-4-5-6 shift pattern for false-neutral avoidance
  • Shaft material is 9310. gears material is 8620. very large 8.125 diametral pitch gear teeth. the gear teeth are 2x circumferentially thicker than stock. tooth flanks are finish-ground after heat treat on a state of the art grinder. agma class 12 gears.
  • Housing is all billet construction from 6061-t651 aluminum. we start with 95 lbs of aluminum and end up with 17 lbs of case and 78 lbs of chips.

The small front wheel drive cars at GM® like the Cavalier® and Cobalt® have a Getrag F23 manual transmission with a center distance of roughly 3.0”*. Bert designed this transmission for GM. The torque capacity of that unit is 165 ft-lbs. The Tremec (Borg Warner-based) T56 that goes in the Corvette® has a center distance of roughly 3.75” and has a torque capacity of 450 ft-lbs. By increasing the center distance 25% the torque capacity increased 173%. A small increase in center distance yields big increases in torque capacity.

All stock Harley® transmissions and aftermarket transmissions have a center distance of 2.5”*. By increasing the center distance 20% to 3.0” the Torquebox conservatively increases the torque capacity to 250 ft-lbs, continuous duty!

In the early Torquebox design stages, the goal was set to design a continuous duty 250 ft-lb gearbox that visually looked like a 450ft-lb gearbox on the outside. We achieved this by taking design cues from classic race-bred American superchargers and not having any excess material, anywhere. We achieved our goal. At Biketoberfest 2005, the Torquebox was unveiled and caught the eye of Kendall Johnson. Regarded as the premier performance engine builder in our industry, he called it “…all business!”.

The Torquebox is available as a 5 or 6-speed, left or right side drive. The 6-speed is identical to the 5-speed except for the addition of two gears and a different drum. The right side drive version is the same as the left except for the mainshaft. All frame, starter, and clutch interfaces are identical to stock 2.5”-based designs. Shift system design innovations and hardware give light, short, precise, crotch rocket type shifts.


BAKER Builder's Kits come fully assembled and ready to install into your existing transmission case with no modifications, shimming, or adjustments required.