Harley 6 Speed Transmission Rebuild - Part 1

5 Speed had a Long Run

The Harley Davidson five speed transmission ran from the early eighties until 2006 depending on the Big Twin model. In 2007 Harley Davidson Big Twin transmissions had undergone a makeover which took us from five gears to the Harley 6 speed transmission.

Better, But…

The Harley 6 speed transmission is excellent, but they do have one week point. The transmission’s main drive gear bearing is a double roller bearing that is prone to premature failure.

Often, as early as 30 thousand miles, the hard- face of the bearing race(s) can wear away, eventually destroying the entire bearing. If you hear a whining sound, especially when coasting; it may be an indication of a failing main bearing. A leaking Harley 6 speed transmission can be another indication, as the main drive gear begins to tip and move out if position within the seal.

Getting Inside

Replacing the Harley 6 speed transmission main bearing is a big undertaking, even for a full time mechanic. The entire gearset must be removed from the motorcycle to replace the main bearing. There are a handful of specialty tools needed to accomplish this job; as well as number of parts, gaskets, and seals, necessary to complete the job correctly.

With the battery disconnected; exhaust and drive assembly completely removed(click here to see video), and the transmission drained, Mike has the 2008 Ultra Classic on the lift and is ready to begin overhaul of the Harley Davidson six speed transmission.

The front pulley nut will be removed next. While removing the retainer; note that the six speed front pulley nut is labeled – RH thread. That means that the nut is normal thread unlike the left handed thread assembly of the five speed transmissions. Loosen and remove this nut with a specialty socket. Then, slacker the drive belt and remove the front pulley.

Next, use another specialty tool to remove the inner primary bearing race. This race must be replaced along with the inner primary bearing. Mike takes the time to demonstrate what can be done to remove a race that has walked its way toward the transmission. He also demonstrates the best way to replace the shift shaft seal for final assembly.

Next, we will be moving to the right side of the motorcycle to begin disassembly of the Harley 6 speed transmission trap door.