Why is my speedomiter not working at all

The speedometer gets speed data from the vehicle speed sensor, which is located on the transmission near the left hand drive shaft flange. Using a diagnostic tool, check for speed data from the vehicle speed sensor. If it's present, then you have a speedometer head or wiring issue there. If it is not present, there is an issue with the speed sensor or related wiring, connector or area. When you say you've "changed everything" -- what is that? And what testing have you done to see what is happening?