I got a 81 Bronco that I am building a 347 for. I'm needing to know what are some of the stock gear ratios that i might have. My Bronco was a 300 6 cylinder. I'm needing to know so that I can get the right cam. Thanks for any help.
There's a couple ways to tell. First, on your door sticker, what does the code say under "AXLE"? It won't tell you straight out, but you can look that code up. Should be something like H14, H16, or where along those lines.
I have an '81 with a 300 6 and my gear ratio is 3.00. If yours isn't, it's probably a 3.5 (which was stock). The easiest way to tell is to jack up the back end of your Bronco, put a chalk mark on the lowest point on both the tire and the driveshaft. Then, turn the drift shaft and count how many times the chalk mark rotates around the driveshaft before the tire does one complete rotation. That'll tell you exactly what you have. (If it's 3 times, you have a 3.00, if it's the 3 1/2, you have a 3.50, if it's a little over 4 times, you have the optional 4.11.)