Speedometer going crazy

I am having a problem with my speedometer working sometimes and then other times it so far off from the speed i am going and all it does is shake from side to side and you can hear is rattling like the cable is loose or something. Any ideas of what i should do is it something i can fix myself or do i need to buy a new cable and take it to a shop?

the cable runs from the back of the speedometer to differential in the transmission. you can check the connection of the speedo gear from the top of the transmission. you'll need to remove the battery, battery tray+washer bottle intake pipe and air filter. then you will see the cable running into the back corner of the transmission. there is one 10mm bolt that hold the gear in. remove that, and you can pry, gently, the gear out of the transmission.

for more info, go here (http://www.stealth316.com/2-speedgear.htm).

http://www.stealth316.com/images/speedgearresting.jpg