DD6: DIRECT DRIVE 6-SPEED BUILDER'S KIT

From an engineering standpoint, it is difficult to design a machine or mechanism that achieves multiple objectives with minimal compromise. An amphibious car is a good example. A few have been manufactured over the years, and they achieved the goal of navigating on land and water, but did neither very well. On the other hand, a Swiss Army knife achieves multiple objectives with minimal compromise. You can snatch the cork out of a wine bottle or kill somebody all with the same widget. The DD6, or Direct Drive 6-speed, combines 3 technical approaches to achieve the most advanced transmission gearset design available for your Big Twin with minimal compromise. First, 1st through 3rd gears are straight cut (spur) for strength during maximum acceleration with no parasitic axial thrust. Secondly, 4th and 5th gears are automotive style helical gears for quiet and smooth operation as highway speed approaches. Lastly, 6th gear is direct drive which means there is no underdrive or overdrive in top gear which translates into 99% efficiency for minimum parasitic loss, minimum wear and tear, and maximum fuel efficiency. But we didn’t focus solely on the gearset, we made this sucker shift like glass. The sequential motion of the hard chrome plated forks is controlled by a fixed spindle radial ball bearing mounted shift drum. Hard chrome guarantees long fork life with minimal imposed friction on the fork groove of the gear. The fixed spindle drum design eliminates any chance of binding or imposed friction about the axis of drum rotation. Drum rotation is controlled by a roller detent and actuated by a BAKER shift pawl with a anti-overshift feature. To make finding neutral an easy chore, we mounted a redundant detent on the left side pillow block.

• Billet 6061-T6 bearing door
• 1/8″ thick bearing retainer plate
• Helical & spur gear design gear for quiet operation
• 28 tooth comprocket forged out of 8620 gear steel
• Regina double row primary chain
• Fat shoe chain tensioner w/hardware
• All transmission seals, gaskets and hardware
• 5 Year limited warranty

 Benefits

• Smoother shifting
• Positive, certain shifting
• Easier-to-find neutral
• Quieter operation
• More-efficient torque-handling

Fitment

• 1990-97 Softail
• 1991-97 Dyna
• 1990-94 FXR
• 1990-97 FLT-FLH
• 1998-99 Softail
• 1998-00 Dyna
• 1999 FXR
• 1998-00 FLT-FLH
• 2000-06 Softail
• 2001-05 Dyna
• 2001-06 FLT-FLH

Bearing Door Type: All DD6 bearing doors have the same outer profile as a stock 5 speed so exhaust brackets, torque arms etc. fit like stock. The DD6 door comes with or without an ear. The ear door is for exhaust bracket mounting and does not fit 1993-2006 FL applications.

Bearing Door
All DD6 bearing doors have the same outer profile as a stock 5 speeds so exhaust brackets, torque arms etc. fit like stock. The DD6 door comes with or without an ear. The ear door is for exhaust bracket mounting and does not fit 1993-2006 FL applications. Note the images below. The DD6 door bearings are larger providing 25% more dynamic load capacity than stock bearings used through 1998, also uses a 1/8″ bearing retainer plate instead of stock style snap rings.

Redundant Neutral System

Shift System
Our 6 Speed shift system with roller detent guarantees smooth shifts every time and our redundant neutral ensures  that finding neutral is a easy chore. We mount a plunger detent on the left side pillow block and cut a plunger track into the shift drum itself.  The plunger follows this track during operation (shifting) and when shifting into neutral pops into a pocket. This system lets you feel that you’re shifting into neutral. No more guessing.  Shift drum features more aggressive timing on the fork groove profiles and is case hardened to 58 Rockwell for wear resistance and crisp shifts. We built our reputation on smooth shifting 6-speed transmissions; our drum designs benefit from the engineering lessons learned. 

FL Case Differentiations
To see an illustrated example of the differences between FL cases by year, please open the PDF here.

Gearset
All DD6 gearsets are made out of 8620 steel, gears are shaper cut before heat treat then precision ground with diamond coated tooling after heat treat (58-62 Rockwell ‘C’). This extra steps ensures not only a quieter gear pair, but enables much tighter backlash control. The gearset is a combination of helical and spur gears to yield silent gear operation. The dog teeth are backcut at a 1° angle to optimize the smooth shift possible, while standard gearsets are cut to a 4° angle.  The mainshaft is unique with 1st main gear being incorporated as part of  the shaft, the countershaft also features a unique 1-piece design with 6th gear.

DD6 Gearset Layout

Gears and Shafts Design

DD6 Shift Forks

Shift Forks
Our investment cast shift forks are made out of 4140 then dipped in a hard chrome plate bath for wear resistance, also designed with oil reliefs to ensure proper lubrication and wear resistance on fork blades and shift dogs.

Available No Cost Options

• Standard Shift Drum (1-N-2-3-4-5-6)
• N1 Shift Drum (N-1-2-3-4-5-6)

Available at an Additional Cost

27T Comp Sprocket, available on FL models for a more aggressive primary ratio. Not compatible on Softails or Dyna models due to the inner primary design. 

The DD6 comes in a stardard 3.24 or optional 2.94 1st gear 

Standard Ratios- shown above are without the 28 tooth comp sprocket

Effective Ratios- shown above are with the 28 tooth comp sprocket

Builder’s Kit Part Numbers

All Part Numbers Listed Are Standard (Effective) Gear Ratios

Builder’s Kit Notes

• The DD6 is available with a 2.94 optional 1st gear ratio for higher horsepower applications. Change the middle numeral ‘1’ to a ‘0’. example: DD401P
• The DD6 is not designed to be used in conjunction with belt drive primaries,auto chain tensioners or easy pull clutch kits.

Complete Build Notes

• The DD6 is available with a 2.94 optional 1st gear ratio for higher horsepower applications. Change the middle numeral ‘1’ to a ‘0’. example: DD401P
• The DD6 is not designed to be used in conjunction with belt drive primaries,auto chain tensioners or easy pull clutch kits.

BAKER Case vs. Aftermarket

Case Design
The BAKER Softail case design had all leak potentials in mind during the design. We added stud pads to the inside of the case so that the thread holes for the transmission studs were blind holes, NOT through holes like some aftermarket brands. Looking at the image on the right you can see the difference. 

Recalibration Box PN 95E-56B

Special Note

• Speedo recalibration unit is required for electric speed sensor applications; PN 95E-56B.
• A + 12MM mainshaft length is available for wide tire applications. (Call us to ensure ordering accuracy)

Compare the DD6

See the difference between other transmission kits and our DD6 and OD6. Click Here for a PDF file comparing our DD6 and OD6 gearset against other manufacturers. 

Click on the image to Compare the DD6 and OD6 gearsets

DD6 vs. OD6

Recommended Upgrade

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 DD6 Fluid Capacity Dry: 22-24fl-oz
• BAKER DD6 Fluid Capacity Wet: 18-22fl-oz

Installation Instructions
DD6 installation instructions with exploded views: Click Here