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Discussion Starter · #1 ·
Let me start by saying I'm not running the gears I should. I know. You don't need to tell me.

I have 3.21 gears on my jku. I have 33" duratracs on. It's fine. It's not the dog everyone says. I can still use 6 th gear on the highway.

My question is, last weekend I was doing some wheeling and I came across a few situations where I wanted to go real slow, but could have used a few more rpm.

I have a 6 speed. In crawling situations I would be in 4 lo. 1st gear. It would crawl over pretty much anything on the easy trails.

Last weekend I was doing more advanced trails than I have before. I found myself wanting to use more clutch to get the rpm up but the speed down. But I don't want to burn my clutch. I was on an incline. I wanted the rpm up. Installed a few times but if I got on the gas any more it would have sped up too much.

I know a regear is in my future. Probably to 4.10. I'm saving up some money now.

Will this allow a slower crawl? If so then it should allow me to run a higher rpm at a lower speed. Right?

Or am I just way off here?
 

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You have it right. At the same RPM, same gear, you will go slower after you regear.
 
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Right. Everyone always thinks of the effect regearing has on rpm at highway speeds in top gear. But regearing has an effect on every gear.
 

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Grab yourself a multi-gear mountain bike.

Put in a high gear and try to go up a hill.

It's hard as hell to pedal up a hill. On flat ground, it'll go pretty fast with moderate pedaling speed.

Now put it in the lowest gear. You can breeze up a hill with little effort, though you will have to pedal really fast to maintain speed.

Differential gearing works the same way. RMS go up, speed goes down, low end power goes up.
 

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If you are already in 4 low, your transfer case is 2.72:1 ratio... your differentials are 3.21:1 ratio. So your effective ratio is based on both of these (not to mention what actual transmission gear you are in).

So... yes.... upgrading to 4.10 in your differentials will change the ratios for both hi and low range for the transfer case. But, if you are happy with the on-road performance, you could also look at replacing the transfer case with a 4:1 unit (from a Rubicon). This would increase your RPMS's more than 40%. Going from 3.21 to 4.10 differentials is going to give you about a 25% bump.

This is always where manuals/automatics get into fights... crawling with a manual is difficult without a really, really low crawl ratio. I mean the kind you just let out the clutch with no gas needed at all...

If crawl is your goal... consider the transfer case ratio first...
 

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Discussion Starter · #6 ·
If you are already in 4 low, your transfer case is 2.72:1 ratio... your differentials are 3.21:1 ratio. So your effective ratio is based on both of these (not to mention what actual transmission gear you are in).

So... yes.... upgrading to 4.10 in your differentials will change the ratios for both hi and low range for the transfer case. But, if you are happy with the on-road performance, you could also look at replacing the transfer case with a 4:1 unit (from a Rubicon). This would increase your RPMS's more than 40%. Going from 3.21 to 4.10 differentials is going to give you about a 25% bump.

This is always where manuals/automatics get into fights... crawling with a manual is difficult without a really, really low crawl ratio. I mean the kind you just let out the clutch with no gas needed at all...

If crawl is your goal... consider the transfer case ratio first...
Thanks for the input. This is something I will definitely consider.
I'm really not sure what I want to do though.
When I'm ready for new tires I might step up to a 35". Then I will definitely need to regear for on road use. My 33s aren't a dog but they aren't a mustang either. With 35s I know I'm going to have issues.
That's why I'm considering going to 4.10s now. I figure it will set me up to be ready for the 35s when I need them.

I only take my jeep off road maybe 3-4 times a year. So I don't want to make a major investment based on that kind of usage. A regear will cost me probably $1,500. If I'm looking at bigger tires in my future I would say the most bang for my buck would be the diff regear and not the transfer case.
 

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Thanks for the input. This is something I will definitely consider.
I'm really not sure what I want to do though.
When I'm ready for new tires I might step up to a 35". Then I will definitely need to regear for on road use. My 33s aren't a dog but they aren't a mustang either. With 35s I know I'm going to have issues.
That's why I'm considering going to 4.10s now. I figure it will set me up to be ready for the 35s when I need them.

I only take my jeep off road maybe 3-4 times a year. So I don't want to make a major investment based on that kind of usage. A regear will cost me probably $1,500. If I'm looking at bigger tires in my future I would say the most bang for my buck would be the diff regear and not the transfer case.
Personally i dont think 4.10s are really adequate for 35s. You should be looking at 4.56 minimum or 4.88 depending on where you live and how you wheel. Probably 4.56 for you.
 
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Basically it makes your driveshaft turns more effective. I would do no less than 4.56, jumping to 4.10 does not justify the cost. 4.88 would be nice too.
 

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My understanding is that you set up your differential gears to handle your top speeds and then your transfer case to handle your crawling.

The diff gears will obviously benefit crawling as well, but that's not really the goal.

So... given your tire size and the fact that you drive on roads, you choose your diff gears. Then see what it's like in low gear for crawling. If it's still too tall, then you look into a different transfer case.
 
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