converting geared hubs to 12.1k gears

[kmalcom]

I am wanting to replace the input gears for my hubs to the 12.1k style. Do the lower dears have to be replaced too ?

thanks

 

[Retiredwarhorses]

No

 

[kmalcom]

ok great... on the lower gears there are two different part numbers also. If I needed to replace one of those should I go ahead and get the 12.1k gears ?

 

[Retiredwarhorses]

ok great... on the lower gears there are two different part numbers also. If I needed to replace one of those should I go ahead and get the 12.1k gears ?

12k has 2 lower gear part numbers because there are straight cut gears and Helical cut gears.
only the late style use helical cut, you can just use what's already in there, no need to change them.
the lower gear is no diff, it's the upper gear that changes.