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NP 241-J transfer case Crawl Ratio

13K views 9 replies 8 participants last post by  BubbaDuss 
#1 ·
Yes, I know it is 2.72 - 1 but what I am wondering if anyone makes a kit to improve on that. I have been looking around for a Rubicon t-case but haven't had much luck. This is when I thought to myself that maybe I was going about this the wrong way. Maybe someone has a low range gear kt for this and I can just tear it down over a weekend and BOOM, a 4-1 low range. I would like to do a 2 wheel low range kit as well.
Does anyone know of anything out there that will do this?
 
#2 ·
I don't know that there has been a transfer case that would do two low since the days of the twin levers.

The crawl ratio of a stock Jeep varies from 31 to 50 for a non-Rubicon and from 55 to 75 for a Rubicon. The crawl ratio is the gear ratio x transfer case ratio x differential ratio. For the automatic the low gear is 3.588 the most common diff ratio is 3.21 and the transfer case as you said is 2.72 for a non Rubicon. Multiplied together you get 31.3

I don't know that you can change the gears in a given transfer case or the transmission. Most changes like that are done either in the differential or by changing transfer cases.
 
#6 ·
If you have the 42RLE auto transmission you can do a Rubicrawler from Advance Adapters. They are the ones that make the Atlas transfer cases, so their stuff is known to be really good. It gives you a second lever with 1:1 and 2.72:1 ratios. It would give you the same 2.72:1 low ratio the regular Wrangler has in 2WD. It would also give you an extra low 7.4:1 while keeping your 2.72:1 in 4WD as well.

I have one in my JKR, so it actually gives me 1:1 and 2.72:1 in 2WD, and 1:1, 2.72:1, 4:1, and 10.88:1 in 4WD.

 
#7 ·
There isn't anything to change the low range in the non-rubicon transfer case.

If you have an 07-11 automatic, you can use the Advance Adapters Rubicrawler: RubiCrawler | Advance Adapters

You can swap in a Rubicon transfer case to get the 4:1. If you can manage to get one that is. It is a bolt in swap in a weekend. You will need to reprogram your computer to know about the different low range.

Beyond that, you can swap in an aftermarket t-case like an Atlas (both 2 and 4 speed). The 4 speed works with all 07-11 JKs but only manual transmission on the 12+ because the computer can't figure out how to shift the transmission with the 4 speed transfer case.

I just got done installing an 11.70:1 4 speed Atlas in my manual transmission 2012 JK. It's fairly expensive but the super low is really amazing.
 
#8 ·
Thanks for all the advice everyone. I was really hoping someone made a low range gearset for my case but it appears that this won't be that easy. I will continue my search for a compatible Rubicon case and dream about the offerings from Advanced Adapters.
 
#9 ·
I looked for a Rubicon case for 2 years. All the while saving up the cash. Once I had enough for an Atlas, I got one of those instead. Keep in mind, you will want new drive shafts if you're going with an Atlas, especially if you go with a 4 speed. So you have to factor that into the budget as well.
 
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