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

4-cyl 33’s and 4.88, 4.0 35’s and 4.88 are good combos for on and off-road performance.

Engine size/power, auto vs 5-sp vs 6-sp, tire size, type of road driving performance/gas mileage, type of off-roading performance desired/crawl ratio. Lots of factors and personal preferences to be considered. Gear selection after increasing tire diameter is probably the most important (and vexing) decision you will be making when modding your Jeep.
 
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I just swapped my rear axle to a Dana 44 and 4.88 gears to go with my 4.0 5 speed and 33's. I could not be any happier. 65 mph and 2500 rpm. Prior to the swap I was debating whether to go to 4.56 gears. I found a Dana 44 with the 4.88's and the choice was made for. 4.88's with my 33's and a 5 speed are awesome. Best money I've spent on the TJ.
 
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I'm going to take the advice that was given to me before for now, but I do have a question.

The 32RH and 42RLE have fairly similar gearing in 1st-3rd gear, which is where I thought most people would be in off road anyway. Is 5.13/5.38 recommended for the 42RLE just because of the .69 OD? While the 32RH is recommended at 4.10 because of the lack of the OD gearing?
 
TheShakes90 said:
I'm going to take the advice that was given to me before for now, but I do have a question.

The 32RH and 42RLE have fairly similar gearing in 1st-3rd gear, which is where I thought most people would be in off road anyway. Is 5.13/5.38 recommended for the 42RLE just because of the .69 OD? While the 32RH is recommended at 4.10 because of the lack of the OD gearing?
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The final drive gear is the one to pay attention to. This is why those two autos cannot be equated to each other.

Also, gear for the highway. If you do that, you will end up with a good off road gear regardless. People who don't regear deep enough sell themselves short on both ends of the spectrum.
 
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Anyone know what the deepest ratio is for the LJ Rubicon dana 44 axle without changing stock carriers or stock lockers? I have 4.10's now, can I go to 4.56 or 4.88 or even 5.13 or 5.38 without adding in the cost of new lockers?
 
bluejeep said:
Anyone know what the deepest ratio is for the LJ Rubicon dana 44 axle without changing stock carriers or stock lockers? I have 4.10's now, can I go to 4.56 or 4.88 or even 5.13 or 5.38 without adding in the cost of new lockers?
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5.38 thick cut gears
 
JMT said:
@Chris, …….. with NSG370 (6-Speed) and 33’s. My RPMs at 70mph with 4.56 is 2850.
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FYI - Interesting point here -

I've been wondering about the accuracy of the grimm jeeper chart based on true rolling radius (measure from ground to center of axle).

If I enter 33" on the grimm jeeper calculator, and 70 mph with 4.56's, it gives me 2730 rpm.

The specs you state above -, 70 mph at 2850 rpm, correspond to a 31.5" diameter tire, or a 15.75" rolling radius out of a 33" tire, due to true sizing and squish (not a true circle at the bottom).

Maybe this is just splitting hairs...…...just saying.
 
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Grimmjeeper is very accurate if you give it the correct tire size. Most don't do that.

The correct size is the hub height x2. Or you can very accurately reverse calculate your tire size if you know the engine rpm for a known speed and gear ratio.
 
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this is the first time I've seen 4.88 for 33's and 5.13 for 35's

I've always thought 33 = 4.56, and 35 = 4.88

I'm referring to 4.0L, with the NV3550
 
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Vasq said:
this is the first time I've seen 4.88 for 33's and 5.13 for 35's

I've always thought 33 = 4.56, and 35 = 4.88

I'm referring to 4.0L, with the NV3550
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That was the old thinking. There was a time when 4.88 was as deep as one could go on a TJ. With 35s being the largest practical tire one should run on stock axles, the flawed thinking assumed that each subsequently smaller tire ought to have the subsequently higher gear ratio. Our options are broader these days, as is our thinking on the matter.
 
jjvw said:
That was the old thinking. There was a time when 4.88 was as deep as one could go on a TJ. With 35s being the largest practical tire one should run on stock axles, the flawed thinking assumed that each subsequently smaller tire ought to have the subsequently higher gear ratio. Our options are broader these days, as is our thinking on the matter.
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I'm all about broader thinking o_O but I just want to get my new information straight..
If I want 33s (or 32s) I should have 4.88 gearing, and it will be very pleasant for a jeep that sees just as much city/freeway use as it does exploring off the beaten path. And if I want 35's I'll want to jump to 5.13 gearing to get the same results?
I was planning on doing 33's next. One day I'll want 35s as an "end all" tire size for my TJ but I don't want to open the can of worms of upgrading all the other associated systems at this time.

thanks for taking the time to confirm these things for me (y)
 
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I run 4.88 on 35s (5speed nv3550 trans) , and I find it to be a perfect combo. I do highway/city cruising. At 70mph, I'm at 2650 rpms. When I'm off road, it's plenty deep enough to crawl. If I was running 33s still, I'd stick with the 4.56.
 
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Vasq said:
I'm all about broader thinking o_O but I just want to get my new information straight..
If I want 33s (or 32s) I should have 4.88 gearing, and it will be very pleasant for a jeep that sees just as much city/freeway use as it does exploring off the beaten path. And if I want 35's I'll want to jump to 5.13 gearing to get the same results?
I was planning on doing 33's next. One day I'll want 35s as an "end all" tire size for my TJ but I don't want to open the can of worms of upgrading all the other associated systems at this time.

thanks for taking the time to confirm these things for me (y)
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Ideally, you would look at grimmjeeper.com and figure out where you want the rpms to be. I am liking mine at 3k/75mph.
 
jjvw said:
Ideally, you would look at grimmjeeper.com and figure out where you want the rpms to be. I am liking mine at 3k/75mph.
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I was looking at that website. so my question regarding that would be, is my NV3550 a "close ratio" or "wide ratio"? or how would I find that information out? both of those are In the drop down options on that site. there's also a NV3550HD which I'm assuming I don't have.
 
Vasq said:
I was looking at that website. so my question regarding that would be, is my NV3550 a "close ratio" or "wide ratio"? or how would I find that information out? both of those are In the drop down options on that site. there's also a NV3550HD which I'm assuming I don't have.
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Close ratio

4:1 first
.78:1 OD
 
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