There is no guarantee you can swap them some have a male into female fitting some the opposite, your felt one is probably a 12mm from the non drive-side, (if its the same as my one) if it is the freehub is generic junk mainly due to a poor(porous?) drive-side seal Ive removed and flushed/ relubed that sucker 1/2 dozen times, its now my back up wheel. What leads you to believe it is a freehub issue and I doubt it has anything to do with your front shifting woes