I think my rear hub may be bad, can I fix it?

[Ghostpunkkilla]

When I'm pedaling or coasting I hear/feel this consistant rythmic thock-thock-thock comming from the back of my bike. I looked at it a little close last night when I was mounting my new tires. Everytime I hear the "thock" noise I see the chain tighten up a little then slack back (if you can picture that, not sure if I'm explaining it well). It's way more noticable with the new tires since I'm running 110 PSI. Is my rear hub toasted or could I maybe take it apart and clean/regrease it. Only thing I know about it is it has an "SX" logo on it. Thoughts? I tried a search but came up with nothing.

Thanks

[Jerry Garcia]

look up the chain from the very back of the bike, does it go straight to the sprocket? Is the hub a cassete with a removable cog? If so maybe you put the lock ring that goes over the cog on backwards?

[Ghostpunkkilla]

If I remember correctly when I was messing with it last night the chain is straight. I have no idea whether or not the cog is removable though, would it be better just to replace the the lock ring if it is?