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Higher crawl ratio? 150:1?


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Hey guys wanted to know how many of you have doublers, crawl boxes, underdrives or even special transfer cases like an atlas to get higher crawl ratios. I mainly want to do this so the jeep can tackle more terrain easier and so its easier offroading with a manual.

Right now, how my comanche is set up: 3.55 gears, ax15, and np231 my crawl ratio is at about 37:1. When I regear to 5.13s crawl ratio is gong up to 53:1.

The main goal is to get around 150:1 as a final crawl ratio but anywhere close to 100:1 is acceptable.

 

What caught my attention was making a crawl box out of the front half of an np231. A company makes an adapter to make the front half of one np231 a crawl box and then mate a second np231 behind that. For a low-low of 7.4:1.  Which when paired with the 3.83 1st gear of the ax15 and the 5.13 gears gets you a crawl ratio of 145:1. Almost exactly what I want. Do you guys think its a viable plan?

 

Here Is the Adapter: NP231 Doubler Adapter

 

and it would look something like this

cqEfcqCl.jpg

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I run a Behemoth crawl box in front of a built 231 in my MJ, with an AX15 and 5.38s it puts me around 152:1

 

Functionally my box works identical to the 231 crawl box that Kris is selling in the link you posted, mine is just a bit fancier.

20141109_184557_zpsc0f2f9b4.jpg

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Just now, johnj92131 said:

How about just using a 4:1 ratio in your 2nd 231 and keeping the 3.55 final drive?

 

My math says it gets you a 147:1 ratio.

A 4:1 in a 231 has a hard time staying together in a single case, the weak planetary would be a grenade in a doubler set up.

26094-add3 (2).jpg

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5 minutes ago, johnj92131 said:

How about just using a 4:1 ratio in your 2nd 231 and keeping the 3.55 final drive?

 

My math says it gets you a 147:1 ratio.

 

I have to re gear anyways for the bigger tires, but people have had issues with the 4:1 low range in the np231

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8 minutes ago, mnkyboy said:

I run a Behemoth crawl box in front of a built 231 in my MJ, with an AX15 and 5.38s it puts me around 152:1

 

Functionally my box works identical to the 231 crawl box that Kris is selling in the link you posted, mine is just a bit fancier.

20141109_184557_zpsc0f2f9b4.jpg

 

Looks fancier too haha. but after checking prices, it may be cheaper to go with the behemoth box

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The Behemoth is a nice box, downside is Jacob at Behemoth has had some big issues with getting product out so it may take a while to get it.

 

The other option is the NW fab ECO box, It's a little more money but they will be much easier to deal with.

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I have an NWF Ecobox (and a NP205F).  With the exchange the way it is, just order one of them, IMHO.  Don't bother with Behemoth, there's lots of guys he owes money to that will likely never see their orders...

 

I'd not recommend a 231 as the second tcase.  NP241DLD would be a better choice if you want to stick with a 2.72:1 chaindrive tcase.  You could steal the planetary from your current 231 to put in the Ecobox and only be out tracking down a 241.

 

Oh, the Teralow 4:1 kit for the NP231 is history.  It was always garbage, but the availability of better options have completely killed their market.

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My 231 has been ok behind the crawl box so far but it has a SYE, 1.25" chain and 6 pinion planetary so It's basically running 241 guts.

I wouldn't want a stock 231J behind a crawl box but some people get away with it for a long time.

 

Behemoth seems to be doing much better than they were before Jacob vanished for a while, but they still have a lot of work to do. My brother has ordered some stuff recently and everything has shown up as promised, but it took forever to show up and came with the usual list of excuses that Behemoth is known for.

 

NWF has been on point with everything he has ordered, definitely the better company to deal with.

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Out of curiosity does it affect your driveline angles a lot? I was thinking about one throwing one in the xj but worried that it would jack up the angles and cause me to stretch the wheel base to compensate. Not to having a longer wb would be bad just more work down the road. 

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It will typically lengthen the front shaft and shorten the rear shaft, how much depends on the crawl box/t case combo you go with.

 

On an XJ that already has a very short rear drive shaft i think you would want to stretch it a bit to help make up for the crawl box.

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3 hours ago, Smokeyyank said:

Out of curiosity does it affect your driveline angles a lot? I was thinking about one throwing one in the xj but worried that it would jack up the angles and cause me to stretch the wheel base to compensate. Not to having a longer wb would be bad just more work down the road. 

 

With the Ecobox/NP205 it's very similar to stock lengths.  YMMV, I have a D60 and a 14 Bolt in it and the front axle is a few inches forwards and the rear an inch back.

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Maybe I missed it, what size tire are you planning to run?

 

I use a NV3550 (4:1 1st), Dana 300 (w/ 4:1), and 4.56 gears.  About 73:1 low/low and run 35" tires.  This is in my CJ7.  I off road quite a bit and have yet to be in a situation where I wanted lower gearing.

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You definitely want a full SYE kit for the strength upgrade, the stock output is pretty weak, a doubler would be really pushing it past its limits.

 

I used cable shifters from JB Custom Fab, i set them into the floor when i made the new tunnel for the flat belly/tummy tuck.

20170615_180023.jpg

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I've been dying to make use of the 231 and/or 247 that have been sitting in my basement for a decade... but by the time you buy somebody's kit, shifters, new prop. shafts, an SYE, and all the other bs you're bound to need you're in for damn near $1,500 :crazy: 

I really wonder if I should try and make my own...  

 

Anyways good luck with your decision.  Sounds like there's plenty of options.  

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On 6/24/2018 at 9:45 AM, mnkyboy said:

That's correct,high/neutral/low.

Oh okay awesome thanks Mnky

 

23 hours ago, A-man930 said:

I've been dying to make use of the 231 and/or 247 that have been sitting in my basement for a decade... but by the time you buy somebody's kit, shifters, new prop. shafts, an SYE, and all the other bs you're bound to need you're in for damn near $1,500 :crazy: 

I really wonder if I should try and make my own...  

 

Anyways good luck with your decision.  Sounds like there's plenty of options.  

yeah I am thinking about going this route or just getting an atlas. Still have a lot of thinking to do, as my manche is going to sit still december unfortunately

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24 minutes ago, Swampy said:

yeah I am thinking about going this route or just getting an atlas. Still have a lot of thinking to do, as my manche is going to sit still december unfortunately

 

Well I knew the Atlas was pricey but damn!  Even the 2 speed is gonna push $3k

 

 

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