If you are regearing your Jeep Wrangler you will want to determine the best gear ratio to use. There are many choices and it is hard to tell what is best when you have some people telling you one thing and others telling you something else. The calculator below will give you an idea of what your engine RPMs will be running at any combination of gears, tires, and transmission. Hopefully this will help you to decide how best to regear your setup.

How to use the calculator

You will need to fill in the fields based on your desired setup. The last field is the gearing options. In order to get the best ratio for your Wrangler you will want to play with this until you get the desired RPMs. The RPM range that is typically accepted as best is between 2000 and 3000 for the 4.0 L HO engine.

When I created this calculator I was running 33s with 3.73 gearing. I also have a 42RLE automatic transmission. If I was going about 45 mph on flat I would get a vibration caused by being in OD with RPMs that were around 1250. This vibe and engine lugging will last from about 1250 to 1750 RPMs. This is an overload of the gearing and is bad for pulling power. This is about the worst I would get with my setup. I could still get around but I would regularly turn off the OD which would help but I would still fall into what I explained above.

To get back to stock gearing get the RPMs that occur with your stock tires and gearing and check at 70 mph. With my 30 inch high tires 3.73 gearing in OD at 70 miles per hour I get about 2000 RPMs. To get back to stock with 33's I need 4.11 gearing. Most people don't want stock gearing though if they are going to be offroading with it. I am going with 4.88's. Mostly because I will be going to 35's when these 33's wear out.

Tire Height:
MPH:
Trans :
Gearing:

RPM: