Determining your rear-end gear ratio.
The only 100% accurate technique is to count the # of teeth on the ring and pinion gears, and divide them.
Need to figure out your rear end gear ratio without actually counter the teeth on the gears? Here's a reasonable technique:
- Put rear on jack stands (safety first!)
- Wrap a long cable tie around the driveshaft, but don't cut the 'tail'. Point it straight up at the 12:00 position.
- Put a mark on a tire, like at 6:00 position.
- Put the trans in Neutral.
- Turn the wheel exactly 1 revolution, noting how many times the driveshaft turns by watching the cable tie. The key is to be as exact as possible.
- Note the position of the cable tie tail.
Now, if the cable tie made 3 revolutions, and is at about the 1:00 position, then it's likely a 3.08 gear. 3.5 revolutions, then a 3.55. 4 revolutions, 4.10, etc.
Not 100%, but should get you close. The bummer is that it'll be difficult to tell a 3.23 from a 3.31, etc.