Recently I had my truck towed to have it's fuel pump replaced. After the replacement the mechanic informs me that my truck isn't shifting and the speedometer isn't working and wanted to know if I had problems with this in the past, I hadn't. He's had my truck for the better part of a month and has tried replacing the speed sensor, the wiring harness, the computer, checked the reluctor wheel, and swapped out the control panel. He says that even after checking all of this and finding nothing wrong my truck will randomly work fine and at other times not shift with the speedometer not working. He's stumped and I'm out a truck. Any ideas?