Right. You need a freewheel tool. It is a four pronged tool with a hex on the end to get a spanner/vive on. Put it into the slots on the freewheel and use your wheelnut to nip it on, mind only nip it, or else the freewheel wont be able to thread off. Nezt jam the tool in the vice HARD. Then turn the wheel anticlockwise and the freewheel should come loose (it will be very tight). then take your wheelnut off and screw the freewheel the rest of the way off with the tool by hand. Then buy a acs Welded freewheel if your on a budget, (a tensile or tryall if your not) and screw it on clockwise by hand making sure that its straight. if it goes tight, take it back off and start again. when it nips on the end of the thread put your bike back together and pedal slowly and it will fully tighten the freewheel(Y) Hope this is a help John.