Ford Repair: Speedometer repair, speedometer repair, speedometer cable

Question
The needle on my speedometer on my 1990 Mustang convertible bounces up and down. This problem has been going on for at least two years.  When the weather is warm it starts working okay again. It just failed inspection and I've got 45 days to get it fixed or they will revoke my registration.  I've seen some info on the internet that it might be the speedometer cable but I don't know how to get to the cable. It said it might only need to be oiled or be totally replaced. I have the Chilton repair manual but it doesn't explain how to get to the cable.  I took it to a mechanic last year and they wanted $500. to replace the speedometer. I would like to try to fix it myself.  I don't know much about repairing cars but am willing to learn.  Any help will be appreciated. Thanks.

Answer
The speedo cable runs behind your speedometer, all the way down to the transmission. In order to replace the cable, the speedometer, will have to come out a little. Its connected on the back side of the gauge. If you want to try oiling the cable you can add some, to the cable, and give it a try. Otherwise, if this doesnt stop the bounceing, then  the cable will need to be replaced.