Re: speedo pulse
your drive and driven gears could also be worn...i would try the above suggestions first.
If you get through them, and also replace the gears as i suggest (last home mech solution) then the speedo itself is crook
You could however start at the speedo unit, and have it repaired by a reputable place (most major cities have at least one), only to find it wasn't the unit but the cable or gears.
You are in a veritable minefield....start withe the cable, it is easily home mech serviced.