Originally Posted by
cxwrench
I don't think you can swap the freehub from any one D/A hub to any other.
Yes, I know that the Fh-7700 has a unique freehub body, ones that inserts deeper into the hub shell. There are other non-DA that could possible work with this deeper insertion requirement. See the FH-6500 and FH-6700. Those are standard steel bodies.
OP never gave a history of the wheel/hub.
OP seems to have come to the conclusion that the cassette is the issue. Maybe he will figure out why....