I wanted to make a thread about recommended gear ratios to help out fellow TJ / LJ owners. My reason for this is because we see this question come up all the time, and it could be helpful for new owners to have a thread like this to reference. Those "gear ratio" charts you see floating around the internet are notoriously inaccurate, especially when you consider that they don't take two of the most important factors into consideration: which engine you have, and which transmission you have. Those factors are absolutely crucial (along with tire size) when making a decision on which gear ratio to go with.
6 Cylinder Engines
Keep in mind that the deepest gear you can put in a non-Rubicon model Jeep is a 5.13, while the deepest gear you can put in a Rubicon model Jeep is a 5.38. This chart only covers up to 35" tires, and the primary reason for this is because with 37" tires or larger, you should no longer be running stock axles at that point, and therefore your gear ratio limitations will change. The table below is laid out by tire size in the left hand column, and transmission on the top row. Match up your transmission with your tire size to determine the appropriate gear ratio.
| 32RH | 42RLE | AX15 | NV3550 | NSG370 |
|---|
30" |
3.73 |
4.56 |
4.10 |
4.10 |
4.10 / 3.73 |
31" |
3.73 |
4.88 |
4.10 |
4.10 |
4.10 |
32" |
4.10 |
4.88 |
4.46 |
4.56 |
4.56 / 4.10 |
33" |
4.10 |
5.13 |
4.56 |
4.56 |
4.56 |
34" |
4.56 |
5.13
5.38 (Rubicon models) |
5.13 |
5.13 |
4.88 / 4.56 |
35" |
4.56 |
5.13
5.38 (Rubicon models) |
5.13 |
5.13 |
5.13 / 4.88 |
4-Cylinder Engines
Generally speaking, it's not a good idea to go over 33" tires on the 4-cylinder engines. For off-roading purposes it's fine, but if you plan on doing any highway driving, anything larger than a 33" tire on a 4-cylinder is really going to make life miserable. The table below is laid out by tire size in the left hand column, and transmission on the top row. Match up your transmission with your tire size to determine the appropriate gear ratio.
| 30RH | 42RLE | AX5 | NV1500 | NSG370 |
|---|
30" |
4.10 |
4.56 |
4.56 |
4.56 | |
31" |
4.10 |
4.88 |
4.56 |
4.56 | |
32" |
4.56 |
4.88 |
4.56 |
4.56 | |
33" |
4.56 |
5.13 | 4.88 | 4.88 | |
34" |
5.13 |
5.13 |
5.13 |
5.13 | |
35" |
5.13 |
5.13 |
5.13 |
5.13 | |
Which transmission does my Jeep Wrangler TJ / LJ have?
For information on which transmission you have in your Jeep Wrangler TJ or LJ,
please see this post.
Which engine does my Jeep Wrangler TJ / LJ have?
For information on which engine you have in your Jeep Wrangler TJ or LJ,
please see this post.
Which axle gear ration did my Jeep Wrangler TJ / LJ come with?
If you need help determining which gear ratio you currently have, see this thread here:
How do I determine my axle gear ratio?
What RPM do I want my TJ to be at at highway speeds?
Ideally you want your engine to be above 2000 RPMs on the highway. The 4.0 for instance doesn't really start it's power band until past 2000 RPM, so keeping it under 2000 RPM at highway speeds is detrimental to performance, and it can also be bad on your engine (in terms of carbon build up, poor fuel economy, etc.). Do not listen to anyone who tells you that you should be crusing at highway speeds with your RPMs under 2000 RPM. This is completely inaccurate and bad information. I prefer mine to be around 2300-2500 RPM at 65 mph, which I feel is the sweet spot for both fuel economy and performance.
What's with 5.13 and 5.38 gears?
5.38 gears will not fit in any other axle other than the Dana 44 axles. In many cases, 5.13 is recommended above for 35s, when 5.38 would actually be a better choice. However, unless you have a Rubicon model (that has both a Dana 44 front and rear axle), then you will have no choice but to use 5.13 gears, unless of course you swapped in Rubicon axles. Many of you will have a Dana 44 rear on your Sport, Sahara, or special edition model TJ. The issue with that is that while you could fit 5.38 gears in the rear Dana 44, they will not fit in your front Dana 30 axle. Remember, that front Dana 44 axle ONLY comes on Rubicon models.
Do I need to have matching gear ratios in both front and rear axles?
Yes! Your front and rear gear ratios must match! If not, you will do serious damage to your vehicle (unless of course you never engage 4WD, in which case, technically you'd be fine.
How much does re-gearing typically cost?
I've found that re-gearing typically costs anywhere from $1000-$1600 for the labor. I've had it done twice, and each time paid $1200 for the labor. This of course excludes parts. You should expect to pay around $500-$800 for parts in addition the labor.
Which brand of gears should I go with?
I personally always recommend Revolution gears, as they are very highly regarded and run by many of us. The general rule of thumb though is to go with whatever gears your installer / shop will warranty. Often times shops will not offer a warranty on certain brands of gears they have never installed before. For this reason, if you really want Revolution gears, but the shop will only warranty Yukon gears, the smart thing to do is go with whatever the shop will warranty.
Is there a break-in procedure for new gears?
Yes, there is indeed! Though Revolution has recently started making REM finished gears that do not require any break-in period whatsoever. In this case, you want to ask the shop installing the gears what they recommend for break-in procedure, and follow their recommendations to the T. Be very aware that if you do not follow the break-in procedure, there's a very good chance you will damage your gears and have to have them replaced. Those break-in procedures are there for a reason.
Should I attempt to install new gears myself?
Absolutely not. If you are reading this, it means you've likely never done it before, and you shouldn't start with learning to wrench by installing gears. Ask someone like
@AndyG what happened when he attempted to install his own gears. This isn't to say you couldn't teach yourself to do it, but if you plan on getting it right the first time having never done a gear install before, you'd better think again! This is one of those tasks that takes a lot of skill and experience, as there are a number of variables that all need to be very accurate.
Is there a gear ratio calculator I can play around with?
Yes, there is indeed! Check out the
Grim Jeeper Gear Ratio Calculator. It's a very helpful tool that will allow you to see how a given gear ratio will affect your Jeep.
My jeep though is slow enough that it's certainly not worth the expense of a regear unless I was to swap in a RJ HP44 to decrease the DS angle.
