What gear ratio should I install in my Jeep Wrangler TJ / LJ? (and other re-gearing FAQs)

[Pcleaners2]

I can tell you 3.73 is horrible on freeway with 5 speed 31s . 5 th gear is useless

 

[miketheneighbor]

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
31"	3.73	4.88	4.56	4.56	4.10
32"	4.10	4.88	4.88	4.88	4.56
33"	4.10	5.13	4.88	4.88	4.56
34"	4.56	5.13 5.38 (Rubicon models)	5.13	5.13	4.88
35"	4.56	5.13 5.38 (Rubicon models)	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	4.88	4.88
32"	4.56	4.88	4.88	4.88
33"	4.56	5.13	5.13	5.13
34"	5.38	5.13	5.13	5.13
35"	5.38	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 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.

I am running 7.50 16LT Power King tires. They are a tall skinny bias truck tire with a circumference of roughly 100". Could tell me what that translates to in the 30's scale?

 

[Chris]

I am running 7.50 16LT Power King tires. They are a tall skinny bias truck tire with a circumference of roughly 100". Could tell me what that translates to in the 30's scale?

View attachment 144565

I wish I could, but I’ve never heard of those tires before, and the size doesn’t make sense to me. There’s nothing on the sidewall like 275/70R17 or anything?

 

[jjvw]

I wish I could, but I’ve never heard of those tires before, and the size doesn’t make sense to me. There’s nothing on the sidewall like 275/70R17 or anything?

He should measure the hub height and double that number. That is the tire size to be used in a gear ratio calculator.

 

[Chris]

Duh... for some reason that didn't even register in my brain.

Once you have three kids, then you'll understand, believe me

 

[miketheneighbor]

He should measure the hub height and double that number. That is the tire size to be used in a gear ratio calculator.

From the

I wish I could, but I’ve never heard of those tires before, and the size doesn’t make sense to me. There’s nothing on the sidewall like 275/70R17 or anything?

Nope just 7.50 - 16. Old school farmer tires used on the backs of pickups back in the day here in the mid west. Here is a side by side with my summer tires which are 31X10.50R15LT's

@jjvw - you mean from the center of the hub to the ground?

 

[miketheneighbor]

From the


Nope just 7.50 - 16. Old school farmer tires used on the backs of pickups back in the day here in the mid west. Here is a side by side with my summer tires which are 31X10.50R15LT's

jjvw - you mean from the center of the hub to the ground?

View attachment 144626

7.50 is the width in inches, 16 is the rim diameter

 

[Sudo]

How notable would the change be between a 5:13 and 5:38 with 42RLE? Worth the expense? I'd like to go to a 34 or 35 " tire but dont want to sacrifice the crawl speed I have with 33's and 5:13.

 

[miketheneighbor]

Duh... for some reason that didn't even register in my brain.

Once you have three kids, then you'll understand, believe me

Made that measurement on my summer tires and it was spot on 31's. These are 32's. Thanks guys!

 

[jjvw]

...

@jjvw - you mean from the center of the hub to the ground?

View attachment 144626

Correct. With the full weight of the Jeep on the tires. You can also place a tape measure on the ground next to the axle tube. Where the tape touches the axle is the center of the axle and also the center of the hub.

Double this number. This is your effective tire diameter. Nothing else matters.

 

[whitrzac]

NGS370, went with 4.88s on 35s.
70 in 6th is about 2800-2900 on the tac, I haven't plugged in the scan tool to get an exact rpm

If you have a super short SYE, no speedo healer, 4.56 and 35s would make the speedo correct if anyone cares...

 

[posulli]

I have read through this thread and have some questions (first off its been very helpful thus far!). I have an 05 LJ with the stock 3.73 gears, 42RLE, and 33" BFG KO2's. I live in Denver so I deal with mountain passes which this thing struggles on. I have talked to a local well known highly rated shop here (edge automotive 4x4) about regearing and they suggested 4.88's. Is the original chart posted more geared towards rock crawling? Or is 5.13 really the advised gearing for a highway and city driven jeep? This is my daily driver so its sees the city quite a bit, then on the weekends It will occasionally see moderate off-road trails for camping and mountain biking. Given what I have described would you still suggest 5.13's or 4.88s?

 

[JDS123]

I have read through this thread and have some questions (first off its been very helpful thus far!). I have an 05 LJ with the stock 3.73 gears, 42RLE, and 33" BFG KO2's. I live in Denver so I deal with mountain passes which this thing struggles on. I have talked to a local well known highly rated shop here (edge automotive 4x4) about regearing and they suggested 4.88's. Is the original chart posted more geared towards rock crawling? Or is 5.13 really the advised gearing for a highway and city driven jeep? This is my daily driver so its sees the city quite a bit, then on the weekends It will occasionally see moderate off-road trails for camping and mountain biking. Given what I have described would you still suggest 5.13's or 4.88s?

In your situation 4.88's would be worse for just street driving than 5.13's would be. When it comes to street driven jeeps, any gearing that works well off-road will also work on-road. I would go 5.13.

 

[jjvw]

I have read through this thread and have some questions (first off its been very helpful thus far!). I have an 05 LJ with the stock 3.73 gears, 42RLE, and 33" BFG KO2's. I live in Denver so I deal with mountain passes which this thing struggles on. I have talked to a local well known highly rated shop here (edge automotive 4x4) about regearing and they suggested 4.88's. Is the original chart posted more geared towards rock crawling? Or is 5.13 really the advised gearing for a highway and city driven jeep? This is my daily driver so its sees the city quite a bit, then on the weekends It will occasionally see moderate off-road trails for camping and mountain biking. Given what I have described would you still suggest 5.13's or 4.88s?

For 33s and the 42rle, gear as low as you can go.

 

[Lunch Patterson]

So, if I just turn off OD on a 42RLE can use 32RH chart then? I assume that is why it is recommended to gear so high with it? The OD being such a crazy low gearing. I'm just looking at putting 31" tires on my stock 3.73. I don't want it to feel like crap though. I mean according to that chart 3.73 isn't even right for the 29s that are on it, and it squeals tire on accident half the time.

 

[jjvw]

So, if I just turn off OD on a 42RLE can use 32RH chart then? I assume that is why it is recommended to gear so high with it? The OD being such a crazy low gearing. I'm just looking at putting 31" tires on my stock 3.73. I don't want it to feel like crap though.

The 42 has a crazy high OD, not the other way around.

One can certainly not use the OD and pretend to have a 3 speed without overdrive. But if you are going to spend the money on a regear, why not do what you can to make the entire transmission usable? The answer is to gear lower than seems right. The generic charts should be ignored anyway, regardless of the transmission.

 

[Lunch Patterson]

The 42 has a crazy high OD, not the other way around.

One can certainly not use the OD and pretend to have a 3 speed without overdrive. But if you are going to spend the money on a regear, why not do what you can to make the entire transmission usable? The answer is to gear lower than seems right. The generic charts should be ignored anyway, regardless of the transmission.

Definitely! I was just pointing out that the chart is saying the stock gearing in the jeep is completely wrong out the gate. It runs great and gets 20mpg with it for me. The thing still feels like a rocket to me on the 29s. It took a lot of adjusting to not chirp the tires when I start from a stop.

I plan on getting 33's some day. The reason I'm was planning on sticking with 31s was so I could get a feel for the jeep and figure out what mods I feel I need, for the type of wheeling/driving I do. This chart scared me like 31s would be almost undriveable somehow. Then I realized the chart says 29s should be undrivable too if you fill in the blank. I will regear for the 33's when I decide to drop the 5-6k to do the suspension, gears, tires, and stuff right.

 

[jjvw]

Definitely! I was just pointing out that the chart is saying the stock gearing in the jeep is completely wrong out the gate. It runs great and gets 20mpg with it for me. The thing still feels like a rocket to me on the 29s. It took a lot of adjusting to not chirp the tires when I start from a stop.

I plan on getting 33's some day. The reason I'm was planning on sticking with 31s was so I could get a feel for the jeep and figure out what mods I feel I need, for the type of wheeling/driving I do. This chart scared me like 31s would be almost undriveable somehow. Then I realized the chart says 29s should be undrivable too if you fill in the blank. I will regear for the 33's when I decide to drop the 5-6k to do the suspension, gears, tires, and stuff right.

Grimmjeeper.com is a great
way to see what different transmission, the size and gearing combinations will do. It is very interesting to compare the stock TJs with their different transmissions over the years. The 32rh and the 42rle are on very distant opposite ends of the spectrum. And you will be hard pressed to find complaints about the 32rh. Based on this and my own experiences and observations, I strongly believe that a good goal to strive for with larger tires is 3k rpm at 75mph.

 

[Lunch Patterson]

Grimmjeeper.com is a great
way to see what different transmission, the size and gearing combinations will do. It is very interesting to compare the stock TJs with their different transmissions over the years. The 32rh and the 42rle are on very distant opposite ends of the spectrum. And you will be hard pressed to find complaints about the 32rh. Based on this and my own experiences and observations, I strongly believe that a good goal to strive for with larger tires is 3k rpm at 75mph.

I got ya. That is my end goal indeed. 33s and 5.13s. All that extra weight and such needs more torque/keeping the engine in the right band to actually move them. I don't assume stock 29s need a 4.27 or 4.56 gear ratio though as the chart would say. It seems to drive fine. I've not tried a jeep with 29s and those ratios though. I guess on the highway going 75 it does run barely over 2k rpm with them. The powerband in TJ's is 2500-2800 right?. I'm just making sure buying 31s isn't going to make it drive like a dog as I learn what it needs. I just want to understand this dream car I finally was able to get, and I want to treat her right . I'd also prefer not to be disappointed when I drop 1k on 31s, haha.

Edit: Is there any replacement for the 42rle? I tried to do some googling but didn't really see anything.

 

[Steel City 06]

The maximum power is actually at up about 4500 RPM. Obviously you wouldn't want to run that for a long period of time. (Short periods at up to and including redline RPMs are perfectly fine.) But running 3000 RPM all day on the freeway is perfectly fine. 3000 RPM is near peak torque for the engine, and generally does not impact fuel economy with any significance on the freeway. The recommemded gearing for the 42RLE is actually below that 3000 RPM target at most freeway speeds.