Quickly Determine the Ring and Pinion Ratio
Determining the ring and pinion ratio can be done in just a few easy steps. No specialty tools or experience is needed to accomplish this task. What the ring and pinion ratio represents is simply how many times the drive shaft spins for each time the tire completes one rotation.
Tools needed to determine ring and pinion ratio
- Wheel chocks or suitable blocks of wood.
- Jack and jack stands
- Eye protection (optional) and chalk / washable marking stick
Park vehicle on a flat, level surface. Use wheel chocks or blocks of wood to secure the front wheels. Raise the rear of the vehicle using the jack, and secure with jack stands under the frame or rear axle assembly. Put the transmission in neutral.
Using a marking stick or chalk, place a line on the drive shaft and another on the rear end that makes one line with the two. The idea is to determine how many times the drive shaft turns. Also place a line on the inside of the tire at about the 6:00 position.
By hand turn the tire clockwise, using the marks you applied to determine how many times the drive shaft rotates with one rotation of the tire. This will determine an approximate ring and pinion ratio.
Here is an example of how it works. If the vehicle has a ring and pinion ratio of 4.56:1, the drive shaft will rotate 4 and one-half times for every time the tire makes one rotation. This is approximate but will easily determine the difference between a ring and pinion ratio of 4.11:1 or 4.56:1. On the other hand, you may have to pay a little closer attention to detail to determine between 4.11:1 and 3.90:1 ring and pinion ratios.
Always be safe when working on your vehicle. Remember to put the transmission in the park before lowering it back down.
The ring and pinion ratio is critical in matching the power produced by the engine to the pavement in the fashion most suitable to the application at hand.
A few facts about ring and pinion ratios
Changes to ring and pinion ratio and wheel size can affect the accuracy of the speedometer and odometer. The lower ring and pinion ratios are generally used for everyday driving, allowing the engine to work at lower RPM’s affording greater fuel efficiency. The higher the ring and pinion ratio, the faster you accelerate and have a more desirable throttle response. Also, the engine will run at a higher RPM rate and use more fuel.
Selecting the best ring and pinion ratio for your vehicle is a matter of preference. This method of determining ring and pinion ratio is approximate.
If the exact ring and pinion ratio is to be determined, removal of the ring and pinion will be required. Then it is a matter of counting teeth on the gears and some math work.