Help me Understand the 3.21 vs 3.73 vs 4.10 Axle Ratio on JKs - Page 3 - JeepForum.com
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Unread 07-05-2013, 07:52 AM   #31
Mudzilla6661
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wow! I just read this thread and have learned so much about crawling ratios and transfer case vs axle gearing ratios. thank you so much everyone! I have my AEV 2.5 lift coming today and gonna get 35's for it I think I will eventually get 4.88 gears for it, i think I have 3.73 now I have a 2010 islander.

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Unread 07-05-2013, 10:17 AM   #32
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After this thread reappeared , I noticed a reference to the TeraLow kit from Teraflex. This kit, as I understand, will not fit the NP231 JK. It only fits the TJ NP231 version of the tcase.
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Unread 07-05-2013, 03:57 PM   #33
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Quote:
Originally Posted by zenman
So how is it now?
Waiting for a call from N4WD for my re-gear appointment. Once the parts are in they'll let me know. Will keep the thread updated. Right now, I'm expecting about 40% slower crawl in 4L Going over, up, or down an obstacle----and les wear n' tear on my manual clutch. Time will tell.

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Know your angles before approaching obstacles and
follow the general rule of off-roading, "Go as slow as you can, as fast as you must."
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Unread 07-05-2013, 04:05 PM   #34
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Quote:
Originally Posted by RockyClymer
After this thread reappeared , I noticed a reference to the TeraLow kit from Teraflex. This kit, as I understand, will not fit the NP231 JK. It only fits the TJ NP231 version of the tcase.
One of my fellow EOTB.ca club members suggested that I look into that for my 2011 JK---and like you said, not an option. I wonder though, if after my re-gear that if I wanted to crawl even slower....is there is any 4:1 transfer case that would work well on my vehicle?

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Know your angles before approaching obstacles and
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Last edited by TrailRated2011; 07-05-2013 at 04:59 PM.. Reason: minor edit
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Unread 07-05-2013, 04:58 PM   #35
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Gear Ratio Charts are Helpful.

Quote:
Originally Posted by Butterjeep View Post
I would regear your diffs first. Your Jeep will be more enjoyable on road as well. The 3.21's should never be available but many Jeeps never make it off road so a lot of people don't realize the gearing shortcomings. There's a gearing chart (just do a search) that will help you out. I run 3.73's and I feel like I need a regear so I am sure 3.21's are frustrating out on the trail.
All: These are very helpful for decision making---tire size selection.

Charts below for those who have a JK without (3.8L) or with a Pentastar (3.6L).
iphone-bkp-12-june-2017-017.jpg   pentastar-gear-ratio-chart-v1.jpg  
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Know your angles before approaching obstacles and
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Unread 07-06-2013, 07:52 AM   #36
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OP "....is there is any 4:1 transfer case that would work well on my vehicle?"
Well, yes, several options: Swap in an NV241OR (rubi version of the 241) which is what I did five years back, look at an Atlas tcase...others will have some more ideas.
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Unread 07-08-2013, 02:15 PM   #37
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Based on the use you described the Duratrac tires are a great fit for someone from ON. I used them before having my WJ written off and they did great in river mud, gravel, snow, ice, granite/quartz trails, etc... After 35,000km Of year round use I had 3/32nd of wear going aggressive on trails 1-2 times a month. Also, if you ever move to PQ you will not need to buy winter tires. Oh they are OK with load range C at 16psi but really shine down at 12 pr so

Awesome info on ratios in this thread and how driving techniques are affected. Thanks everyone!
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Unread 08-02-2013, 06:21 PM   #38
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Re-gear Results

Quote:
Originally Posted by TrailRated2011 View Post
Waiting for a call from N4WD for my re-gear appointment. Once the parts are in they'll let me know. Will keep the thread updated. Right now, I'm expecting about 40% slower crawl in 4L Going over, up, or down an obstacle----and les wear n' tear on my manual clutch. Time will tell.

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My re-gearing (3.21 to 4.56) was completed and I picked up my vehicle this morning.

Break-in period for the next 500 km. I'll be nice n' easy regular road driving....no more than 80km/hr..

When I got home from work this evening I put it in 4L and approached a very steep incline of -7 ft. rock and grassy hard packed soil. I was absolutely dumfounded. Did not even touch the gas pedal and it crawled ever so slowly up n' over!!! OMG

I've never, I mean never, experienced that type of controlled crawl ever!!!! Could I be dreaming... Heh Heh

The other thing I noticed is that the vehicle is not at all sluggish. When I upgraded my tires from stock OEM to heavier Duratrac 33s----the sluggishness was often noticeable---but I quickly got used to it and until today didn't realize how responsive my vehicle can be!!!!
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Know your angles before approaching obstacles and
follow the general rule of off-roading, "Go as slow as you can, as fast as you must."
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Unread 08-02-2013, 06:54 PM   #39
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Quote:
Originally Posted by TrailRated2011 View Post
My re-gearing (3.21 to 4.56) was completed and I picked up my vehicle this morning.

Break-in period for the next 500 km. I'll be nice n' easy regular road driving....no more than 80km/hr..

When I got home from work this evening I put it in 4L and approached a very steep incline of -7 ft. rock and grassy hard packed soil. I was absolutely dumfounded. Did not even touch the gas pedal and it crawled ever so slowly up n' over!!! OMG

I've never, I mean never, experienced that type of controlled crawl ever!!!! Could I be dreaming... Heh Heh

The other thing I noticed is that the vehicle is not at all sluggish. When I upgraded my tires from stock OEM to heavier Duratrac 33s----the sluggishness was often noticeable---but I quickly got used to it and until today didn't realize how responsive my vehicle can be!!!!
Kudos on the upgrade...

If you had 3.73 would have made the move?

Just wondering?

Thanks,

John
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Unread 08-02-2013, 07:04 PM   #40
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Quote:
Originally Posted by Deuskid View Post
Kudos on the upgrade...

If you had 3.73 would have made the move?

Just wondering?

Thanks,

John
Hi John, regretfully I have no experience driving a 3.73.

My re-gear decision was based on how my JK (3.21) performed off-road. I just couldn't get it to crawl slow enough---a lot of unplanned impacts/bumps---particularly on the undercarriage. Also, my 33" Duratracs were a factor---based on the 3.8L, manual transmission combo.---tire size/axle ratio matrix earlier in this thread.

To me, driving slowly is the key to successful off-road driving, especially over rocks and rugged terrain.

I'll now be able to see what I'm driving over and tiptoe over obstacles with controlled authority.
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Know your angles before approaching obstacles and
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Last edited by TrailRated2011; 08-02-2013 at 07:06 PM.. Reason: minor edit
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Unread 08-02-2013, 07:38 PM   #41
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Good for you-


Quote:
Originally Posted by TrailRated2011 View Post
Hi John, regretfully I have no experience driving a 3.73.

My re-gear decision was based on how my JK (3.21) performed off-road. I just couldn't get it to crawl slow enough---a lot of unplanned impacts/bumps---particularly on the undercarriage. Also, my 33" Duratracs were a factor---based on the 3.8L, manual transmission combo.---tire size/axle ratio matrix earlier in this thread.

To me, driving slowly is the key to successful off-road driving, especially over rocks and rugged terrain.

I'll now be able to see what I'm driving over and tiptoe over obstacles with controlled authority.
Now, in your dreams--imagine 5.38s and Rubi xfer case !!

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Unread 08-02-2013, 07:43 PM   #42
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Nirvana

Cheers+
Quote:
Originally Posted by JIMBOX View Post
Good for you-

Now, in your dreams--imagine 5.38s and Rubi xfer case !!

---NIRVANA--

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Unread 08-03-2013, 10:06 AM   #43
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I have the 3.21 and have been considering a lower gearing (3.73 or 4.10) with my 33" tires, but I am concerned about fuel economy. Yeah yeah I know it is a Jeep and I did not buy it for fuel economy, but every dollar helps! For those that have went from 3.21 to something else, what kind of MPG difference did you see?
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Unread 08-05-2013, 06:59 AM   #44
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Quote:
Originally Posted by Cmp8254 View Post
I have the 3.21 and have been considering a lower gearing (3.73 or 4.10) with my 33" tires, but I am concerned about fuel economy. Yeah yeah I know it is a Jeep and I did not buy it for fuel economy, but every dollar helps! For those that have went from 3.21 to something else, what kind of MPG difference did you see?
Question is, are 33" tires going to be your final size?

Just try to think into the future, because 3:73 is a great ratio for 33's but any larger tire and you will want a deeper ratio.


Also the gas mileage from 3:21 to 3:73 is very minimal.
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Unread 08-05-2013, 08:21 AM   #45
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Any gear ratio deeper than 4.10 is great, even for 33' tires-

The major determining factor is whether or not your jeep is a DD-

Ifit is then you should stay in the 4.88/5.13 range--5.38s are wonderful, but will be a little nerve racking at 75/85 mph freeway travel-

With an auto, the deeper you go the better you fly !

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