JIMS Fat 6 Six-Speed Transmission Gear Set – Big Bearing Trap Door (2006–2017 Harley-Davidson® Big Twin)

1103-0064

Built for riders who demand strength, smooth shifting, and reliability under serious power, the JIMS Fat 6 Transmission Gear Set delivers race-proven durability for high-performance Big Twin applications. Featuring straight-cut gears, increased tooth width, and a billet big-bearing trap door, this is the transmission upgrade your motor deserves.

Key Features & Benefits

• Aerospace-Grade 9310 American Steel
  Manufactured from premium U.S.-sourced 9310 steel for extreme durability and long service life.

• 53% Wider Straight-Cut Gear Teeth
  Significantly increased tooth width compared to stock gears for higher load capacity and improved strength under hard acceleration.

• JIMS® Quick Shift Ring Technology
  Reduces the harsh “clunk” often felt during shifting while delivering positive, precise gear engagement.

• Precision Ground Gear Profiles
  Teeth are ground to exact mating profiles for smooth operation with zero gear whine.

• Billet Big Bearing Trap Door Assembly
  Shafts and gears are pre-assembled into a JIMS® 6061 billet aluminum big-bearing trap door, reducing flex in high-horsepower and high-torque builds.

• True Bolt-In Installation
  Compatible with your stock gear selector — no custom linkage required.

Technical Specifications

• Product Name: Gear Set

• Transmission Type: 6-Speed

• Model: Fat 6

• Application: Big Twin

• Riding Style: Street / Performance

• Units: Kit

Package Information

• Weight: 33.4 lbs

• Dimensions:

  • Length: 20 in

  • Width: 12.25 in

  • Height: 10.25 in

Compatibility & Fitment

Fits 2006–2017 Harley-Davidson® Big Twin models including Touring, Dyna, and Softail platforms.

⚠️ Important Fitment Note (2006–2009 models):
Some models may require a dealer or technician ECU flash for the 6th gear indicator light to function correctly.

Why We Recommend It (High Desert Performance)

If you’re pushing big torque, aggressive cams, or a big-inch motor, the stock transmission becomes a weak link. The JIMS Fat 6 is a proven upgrade that handles abuse, shifts clean, and holds power without compromise — exactly what we trust in high-performance street builds.