Swampy Posted June 17, 2018 Share Posted June 17, 2018 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 Link to comment Share on other sites More sharing options...
johnj92131 Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
mnkyboy Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
mnkyboy Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
Swampy Posted June 17, 2018 Author Share Posted June 17, 2018 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 Link to comment Share on other sites More sharing options...
Swampy Posted June 17, 2018 Author Share Posted June 17, 2018 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. Looks fancier too haha. but after checking prices, it may be cheaper to go with the behemoth box Link to comment Share on other sites More sharing options...
mnkyboy Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
Swampy Posted June 17, 2018 Author Share Posted June 17, 2018 I will definitely look into it. I still have a while before I do something like this, just wanted to get an idea of whats available and what people are using Link to comment Share on other sites More sharing options...
DirtyComanche Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
mnkyboy Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
Smokeyyank Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
mnkyboy Posted June 17, 2018 Share Posted June 17, 2018 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. Link to comment Share on other sites More sharing options...
DirtyComanche Posted June 18, 2018 Share Posted June 18, 2018 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. Link to comment Share on other sites More sharing options...
Smokeyyank Posted June 18, 2018 Share Posted June 18, 2018 Gotcha, thanks for the info. Link to comment Share on other sites More sharing options...
schardein Posted June 18, 2018 Share Posted June 18, 2018 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. Link to comment Share on other sites More sharing options...
Swampy Posted June 21, 2018 Author Share Posted June 21, 2018 Yeah I was planning on swapping in all the np241 guys into the np231 case and using that behind the crawl box. The ecobox does look good I am planning on running 35-37" tires Link to comment Share on other sites More sharing options...
Swampy Posted June 21, 2018 Author Share Posted June 21, 2018 Would you recomend an sye for the second 2 case? Also @mnkyboy how did you/where did you mount the shifter for the crawl box Link to comment Share on other sites More sharing options...
mnkyboy Posted June 21, 2018 Share Posted June 21, 2018 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. Link to comment Share on other sites More sharing options...
Swampy Posted June 24, 2018 Author Share Posted June 24, 2018 Those cable floor shifters look good. This is definetly helping piece together my crawl box/tcase. The crawl box just has high and low right? Link to comment Share on other sites More sharing options...
mnkyboy Posted June 24, 2018 Share Posted June 24, 2018 That's correct,high/neutral/low. Link to comment Share on other sites More sharing options...
A-man930 Posted June 28, 2018 Share Posted June 28, 2018 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 I really wonder if I should try and make my own... Anyways good luck with your decision. Sounds like there's plenty of options. Link to comment Share on other sites More sharing options...
Swampy Posted June 29, 2018 Author Share Posted June 29, 2018 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 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 Link to comment Share on other sites More sharing options...
A-man930 Posted June 29, 2018 Share Posted June 29, 2018 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 Link to comment Share on other sites More sharing options...
DirtyComanche Posted June 29, 2018 Share Posted June 29, 2018 Shop around. There's lots of room to move on the pricing of AA stuff. Link to comment Share on other sites More sharing options...
Swampy Posted June 29, 2018 Author Share Posted June 29, 2018 Well see what happens. Lots of options and lots of time haha Link to comment Share on other sites More sharing options...
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