Will a 2004 road King trans fit on a 2001 road king

 

No help

 

The gear set will but not the case the primary locator dowels will not line up.

 

Why r the primary case the same part number

 

Oops it's not the dowel location its the swing arm pivot shaft hole is a different size. 01 is a 5/8" bore and the 02-06 is 3/4" bore.

 

What will it Hurt

 

The tranny is mounted to the swingarm on FL models. The shaft going through the swingarm on an '01 is 5/8". The '04 tranny runs a 3/4" shaft and you'll need the swingarm for the '04 too in order to do the swap.
The problem there is the '04 swingarm runs the 1"axle and the '01 still runs the 3/4" axle. See the problem?

So as Mark @ Baker Drivetrain previously suggested, swap the gear set only and run the '01 case.

 

The 01 is 5/8. The 04 is 3/4
That little bit what will it hurt

 

It depends upon how long you want to live on your first 70 mph sweeper when the rear wheel is now dictating what direction your motorcycle is headed. How much it hurts depends on what surface you land on (and it there are any trees in the vicinity.)

Try to imagine how much side to side play at the back of the swingarm is caused by a 1/8" slop at the front of the swingarm.

Good luck with your project.

 

I found this at Grangers Bronze Bushing / Bearing 3/4" OD X 5/8" ID X 1 1/8 " long 660 BRZ 4 pcs