How does the gear attached to the cable look when you take it out? I can tell you from a lot of recent experience with the Autometer mechanical speedos they are all destined to fail at some point.
If you want to make a nice upgrade and avoid further issues with speedos and cables you should consider some gauges from
www.speedhut.com ... or I can get them for you. Either way you will avoid the perpetual problems with the Autometer gauges.