Diesel Bombers - CRUISE CANT GET IT FIXED

Hi I have a problem with the cruise control 2001 Automatic . I have done all the checks that I have seen on the site . I have 12 volts at pin 3 when the servo is pluged in. I also have ground at pin 4. No vacuum leaks. Brake switch works it kills the 12 volts to pin 3 when depressed. When power is on pin 3 the other terminals have 12 volts sounds right also. History on Cruise problem work fine pulling great and just dropped off. When I turn on the cruise button the cruise on light comes on dash. But set does not work. I have tried all other items seem to work. Horn , Vol controls work and Radio channel changes. I think the Clock spring is ok. The only error I had after the cruise failed was p0500 vss speed but can't check it out not enough info on it and will not show a code again. Odometer works fine at the time I was towing heavy after the cruise failed and I was parking the trailer and the tires did spin on grass maybe this cause it but every where I read it says the VSS sensor is not used but it is in the transmission seems odd. I have never seen the p0500 error ever sinse I have owned the truck? Just wondering is there any way to prove the Cruise Servo is working maybe ground pins 1 or 2 not sure just want to get the Vacuum to move the cable. Just cant figure it out maybe you have a few more tricks you know of. I was going to try unplugging the rear end speed sensor in the rear end to see if the VSS takes over then it might fail. Any help would be great I am at a lost.