Alright heres the problem:  For the past 6 months my speedo has not worked right.  Some times it will work, but only for about a minute or two.  I noticed that when it does work, my engine will rev at the right RPM (i.e.:  I will be driving down around 65 mph and would be reving at 4500.  When the speedo worked, it will rev normally at around 2500 - 3000.)  I finally changed the the speed sensor and still nothing  

   please, 
H E L P