Speedometer and rpm guages stop working and transmission wont shift

Sounds like you could have an issue with wiring or the vehicle speed sensor itself. This doesn't really explain tachometer issues though. So, hands on testing with a GM diagnostic tool is needed to determine what is going on. You did not indicate which engine your Chevrolet truck has. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops