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Any Ideas About What Could Be Wrong?

Hey Guys, I bought my car back in September and I love it to death but there are a few things that need to be fixed up.
So, my Gauges aren’t working and I am not sure if it;s the gauge itself or the electrical. My Gas gauge and my Voltmeter both work, it’s just my Speedometer and my Odometer that don’t work. Also my Oil Gauge but I know that the whole thing needs to be replaced.
Any help would be great, I plan to take it to a mechanic soon…if they ever call me back.

I don’t know what years firebirds were made, but it seems like it has been 20+ years since I saw a new one, so there is a good chance that your speedometer is mechanically driven. If so, if you can get to the back of the guage cluster, there will be a cable that comes out of the firewall and attaches to the back of the speedometer. It will be stiff and about the thickness of a pencil. It will unscrew from the back of the speedometer. Inside you will find a drive cable that is square shaped at the end where it plugs into the speedometer. Watch it while you drive the car and see if it turns.

If the cable turns, then there is a plastic gear worn out in the speedometer. These are sometimes repairable if you are handy, but you would probably have to cut the speedometer open with a dremel tool.

If the cable does not turn, then the cable is broken or the plastic drive gear in the transmission is worn out. How tough either of those parts are to replace depends upon where the cable attaches to the transmission and whether there is room to get your hand to the cable connection without lowering the transmission.

Put your car up on solid ramps or jackstands before looking at the transmission end.

Thanks! as i said, I plan to bring it to a mechanic close by who works on classic cars. I just wanted to see if I could get some insight before hand.

Sooo what year Firebird do you own? How many miles on it?

it’s a 79’ and when i bought it the wonder said it had 135,000 but i do not know exactly how many. I know the engine was replaced around 98’

The oil gauge problem might not be the gauge itself, but maybe the oil pressure sender has topped working. Not an uncommon thing. That part is usually cylindrical shaped, about 1 1/2 inches long, & screws into the engine block, often near the oil filter. There’s a connector with a wire on it that eventually goes to the gauge. If you have the wiring schematic you can trace the wire colors to find it pretty quickly. You might discover it’s just its connector has come unplugged.

For the oil guage, first find it and remove the wire to the guage and connect it directly to ground on the engine. Then turn on the key and if the guage jumps to MAX oil pressure the guage itself is likely OK as is the wiring and therefore the sender would be the problem.

On the speedometer, remove the speedometer drive cable from the transmission tail piece and connect a drill to the square cable end. have someone watch the speedometer while you run the drill forward then reverse to see if the speedometer needle jumps. The drill won’t need to turn very fast to peg the needle and reversing it won’t cause a problem. If the needle sweeps over the problem is likely the drive gear which is in the cylinder that the cable was removed from. If the needle fails to move the cable is likely broken or if there is a cruise control on the car it could be failng.

The weakest links are the wire and sender on oil pressure and the drive gear and cable on the speedometer. Check those out and post back.