Question on CB77 speedometer

[Steve P.]

I have a 1967 305 Superhawk, only 8000 miles. I just replaced the speedo cable with a new one that matches the old old one perfectly. Now, the speedometer MPH reads about 3- 5 times more than it should. Example, I am only going 10 MPH, it indicates I am going 35-40MPH. It also tops out when i go about 15-20MPH.
It appears the problem is inside the speedo case, perhaps the small intricate gears are out on sync?
I am reluctant to open the speedo case that has the tach and speedo dials.
Any suggestions please! Thanks very much!!!
Steve

[conbs]

Search this site. I think Jensen had a post that talks about loosening the cable where it goes into the speedo. You may be pinching the internals of the speedo which would make it give a high reading.