depends on the year, 07-08 had taller gearing they wont pull a passenger with gear without downshifting. 09^ lowered the gearing and they are much more pleasant to use. the gearing was so tall on the 07 that 5th gave a higher top speed than 6 th.

 

What does this have to do with 6 speed transmission in a Road King?

 

Both transmissions are 1:1 in high gear so highway manners relies on final drive ratio.

 

My understanding is that 5th in the 5 speed is 1:1. Sixth gear in the 6 speed is true overdrive at a 0.89:1 ratio.

 

So the op the gear sets are even more interesting. So 2007 was the first year of the 6 speed in the touring line. the 5 speed. for like 92 -2006 there are upgrades for 6 speeds that are direct drive and over drive and under drive. they can be easily swapped out. has to do with riding style and the engine powering the bike etc.... my evo with 96" stroker would not benifit from a 6th gear with out major cam and compression changes. timing also the 88 and 96 really do not have the torque or power to operate the bike in 6th gear and have it be power full. under drive or over drive can be set up upon engine size. torque, and curve. needs etc... that is why harley upgraded to the m8 and use 6 speeds.

 

OEM 6 speed transmission is a direct drive in top gear, just like the 5 speed.

The main drive gear is coupled to the mainshaft in 6the gear, resulting in a 1:1 ratio.

 

Your understanding is wrong. 1:1 on both 5 & 6 Speed trans. Ratio is determined by primary or final drive ratio...........I/E sprockets used.