Speedometer and gas gauge

[greenWX]

I just got a '73 charger and the gas gauge and speedometer don't work. the gas gauge doesn't read at all even with a full tank, and the speedometer is faster than I'm actually going. I was just wondering how to get a start on this, and how to go about it.

[XH29N0G]

For the speedometer you want to check whether the odometer part is accurate or not.  Hopefully it is that the speedo gear is not correct.  If the odometer is reading accurately, but the speedometer is not, then you will need to get the speedo serviced or buy a new (repop) one from some place like classic. 

For the gas gauge, take a look at the thread on cluster restoration http://www.dodgecharger.com/forum/index.php/topic,37999.0.html You need to determine whether it is the gauge that does not work, the sending unit that does not work, or something in between the two.  The thread I listed should show you how to check the gauge.

Others will have to tell you how to check the sending unit.  If it is out of the tank, you can see how its resistance changes with the position of the float, but I do not know how to check it in the tank.

[csx4590]

To get correct the speedo gear, you need the rearend gear ratio (3.23, 4.11 etc) and the tire diameter. Gear ratio can be found by jacking the rear up and making a mark on the driveshaft. Then spin one of the rear wheels one time around and watch how many times the driveshaft turns (a little over 3 turns would mean 3.23). The tire diameter is measured as if looking from the side of the car, tread to tread across the wheel. Once you have these two numbers, google up "Mopar speedo gear chart" and use the chart to determine what gear you need. Mine was reading way over and after doing the above, I got it to within 1 mph of a digital speedometer I downloaded to my phone. If you can get under the car easily, the gear change is fairly easy and straight forward (google and/or youtube will also show how to do it). You can get the speedo gear at most Mopar selling classic car sites (year one, classic etc). Hope that helps...

[greenWX]

I somehow pulled out the speedometer cable, and after I plugged it in the needle doesn't even move now. What do I do about that.
As for the gas gauge the issued has been narrowed down between the tank and leading up to but not including the fuse box.

[XH29N0G]

I don't think you could have broken it by unplugging and plugging in, so I would continue to see if the plugging in is done correctly.   It should slide in pretty easily, and then click in place. I assume this is the plastic fitting on the speedometer, not the plug into the transmission.

If that doesn't work, you can pull it out and see if the end in the cable spins when the car is moving.  If it is spinning, then you want to look at the speedometer again. 

Others will correct me if I am wrong.