The 1947 - Present Chevrolet & GMC Truck Message Board Network

It's probably more than one issue. For the gas gauge first I'd check the fuse panel and make sure all of them are good. Then it's on to checking the connections at the gauge, and the fuel tank. Attach a separate ground if needed to make sure the circuit is being completed. If you have a continuity tester check the wiring going from the tank to the gauge and make sure it isn't broken somewhere in the circuit. If this doesn't turn up anything it's time to check the gauge and sending unit. If the truck has been sitting for a long time, or the tank wasn't protected, the sending unit can easily be corroded and inoperative, especially if the tank is full of crud.

The speedo/odometer problem is one of three things - the speedo itself, the cable or the driven/driving gears. First make sure the cable is connected to the back of the gauge. If it is, disconnect it and pull it down under the dash so you can see the end. Either jack up the rear of the truck (safely) and run the truck in gear, or just drive down the street, to determine if the cable is turning. If it is, something is probably wrong in the speedo head. If it isn't turning, either the cable is dry or broken, or one of the square ends may be rounded off. This is a common problem on old vehicles that have not been driven in a long time. If it's just dry, pull the cable completely out of the jacket and saturate it with either assembly lube or motorcycle chain grease (speedo cables like being well lubricated). Squeeze it back in to the housing and wipe off the excess. If none of that fixes the problem, pull the driven gear out of the side of the transmission and check the teeth. If the cable has been stopped for whatever reason, it can cause the teeth on the driven gear to be chewed off requiring replacement. Good luck.