Speedometer problem

[Malious]

I have been having a small, but very annoying problem with my speedometer the last few months. For the last year, when in cold weather the speedometer on my 86" BII will wig out on me, saying I'm doing 75mph while going 55mph. The colder it is, the worse it is and will always read faster then I am going, the needle bouncing all around the dial while driving. After about 30 minutes of driving with the heat on full blast it will usually start reading accurate again, and works fine when its warmed up, or in hot weather. Thought this was an odd problem and would like to know if anyone else has had this problem, or has any ideas on what to about it. Thanks guys.

[Mud Addict]

Replace the speedo cable