Originally Posted by
FBinNY
Step one is to isolate the issue to either the wheel bearings, or the freehub ratchet mechanism. That's easy enough to do by simply spinning the wheel in your hand holding the axle and feeling for snags or torque, then putting a finger against the cassette t hold it and seeing if it's dragging against the free-spinning wheel.
While you have it it's also easy to check the axle, by turning the axle in the stationary wheel and looking for oscillation at either ends.
Once you've (I expect) localized the problem to the freehub, then you can continue to try and flush it clear, but otherwise it'll need replacement.
I agree that the first step would be to do a quick inspection like this but even if it looked like the FH was the issue I'd still pull the axle and dump the bearings. Just hosing the FH down with lube to maybe flush it out most probably will just flush out most any of the remaining grease in the bearings as well.
If the initial spinning of the freehub with the wheel out of the bike shows any issue with either the FH or the axle I'd just start by yanking the axle. It could very well be that both the FH and the wheel bearings are both hosed to a greater or lesser and it might be difficult to fully identify the source of the problem without isolating them from each other.
My advise is to find a used replacement FH out of a donor hub. FH's can be very expensive. My local coop has hubs by the hundreds sitting in tubs for about $2 each. That's
much better than $40+ for a new replacement Freehub. The trick is doing the research as to what other hubs use a compatible FH as finding other matching tandem hubs might be difficult.