I have a '67 Firebird with a 326 and 2-speed automatic. When I got the car, the speedometer cable was loose at the tranny connection. I tightened that but still have a problem. The speedometer reads consistently about half the actual speed. In other words, if I'm going about 45 mph, it reads 22mph...if I'm going about 65 mph, it reads 30 or 35 mph. The needle doesn't "bounce" or look abnormal other than the speed is reading about half of what it should. I think everything is original but I'm not 100% certain.

Any ideas as to what this could be or where I should start looking for the problem? I've only had the car a month or so and am still getting familiar with her.

Thanks for any help.