There are two
--no, three-- differences in the hub shell.
First, a track hub has a double thread-- a larger thread for the cog (it is the same thread as a freewheel), and a smaller, left hand thread, for the lock ring. You can put a freewheel on a track hub, and you can put a track cog on a freewheel hub, but you cannot put a track lockring on a freewheel hub.
Second, on the Campy Record large flange track hubs I've seen, the left (non-drive side) flange was on the outside of the bearings, like on a front hub; on the corresponding freewheel hubs, the flange is on the inside of the bearings. This photo shows it rather poorly...
Third,
Originally Posted by
jeirvine
Also no oil ports on track hubs.