A few of my students were asking me how do I know that my 4runner has 5.29 gears without taking the rear end apart and counting the teeth etc..

So I decided to do a write-up after i showed them in class. Sorry If there is another thread on this already.

It really is very simple.

1. Jack the Rear end of the Vehicle up. Obviously make sure that the front or rear wheels are blocked so the vehicle does not move on you.

2. Place the transmission in Neutral.

3. Now Place a Zip Tie or something around the Driveshaft that can indicate a specific point of reference.
- I like to use a Zip Tie and leave the tail on the end so it acts like a pointer.

4. Turn the Driveshaft until the Tail of the Zip Tie is pointing at 12 O'Clock. This is not completely necessary to do. You can point it in any direction, as long as you can verify the starting point.

5. Now Put a mark / chalk line on the tire at 12 or 6 O'Clock. Either one does not matter. Again, just for a reference point.
- I marked mine at 12

6. Now rotate the tire slowly making note of how many times the Zip Tie tail rotates around via the driveshaft.

7. Finally the calculation. Very easy.

- If your driveshaft makes 3 and 3/4 revolutions it would be safe to say that you have 3.73 gears

- If your driveshaft makes 4 turns and stops right around 4:10 it most likely would be a 4.10 gears.

In my case I had 5 driveshaft rotations that stoped a quarter of the way through the next rotation making the Ratio come out to what gears I know that are in my axle which is 5.29.



Please feel free to edit or add any information. Just thought I would share some helpful Info.

 

Here's the "one wheel off the ground" method for open diffs, and the method you've described(which only works for limited slip (LSD or "posi"), locking differentials, spools, etc.).


http://home.4x4wire.com/erik/diffs/#ratios

 

Thanks for the clarification.