Topic: 231 Doubler Crawlerbox

[Jeffy]

http://www.pirate4x4.com/articles/productreviews/mad_rooster

 When planning the build up of my 1992 Wrangler, I decided that one of the key features I wanted was deep crawler gearing. As I looked for a product to fit my needs, and my budget, I found many affordable options for Toyota and Suzuki owners, but nothing available for my Jeep. Then I discoverd Mad Rooster Off-Roads new Plantetary Crawlerbox adapter. Mad Rooster's kit, based on the very common NP231 transfer case was perfect for my buildup. Combining the Planetary Crawlerbox with my AX-15 transmission, Dana 300 transfer case and 5.86 gears gives me a crawl ratio of 160:1, just what I was looking for.



Mad Rooster's Crawlerbox is a surprisingly simple concept. It uses the 2.72:1 planetary gears and 1/2 of the housing from the NP231 and turns it into a crawler. At only 7.5" long the crawler is very compact and light weight. Combined with my Dana 300, the complete package is 17.5" long overall. Compare that to a stock NP231 at 18.5" and the crawler/Dana 300 combo is very attractive, even for a Wrangler's short 94" wheelbase. The Crawlerbox can also be bolted to a 23 spline NP231 case for those with a longer wheelbase, or the crawler/Dana 300 combo can be flipped for use with a driver side differential.

   Included in the kit is the adapter plate, a rotation ring, and a through hardened 4340 chrome moly steel mainshaft. Mad Rooster also includes all the necessary hardware and some basic instructions to help you install your new Crawlerbox.

The first step in installing the crawler is to split the NP231 in half. This isn't as difficult as it sounds. First I removed the nut on the front output. Then I removed the 8 bolts holding the 2 halves together and pried between the halves to break the silicone seal. Once the seal was broken I was able to pull the rear half of the case off. All the parts that I didn't need stayed attached to the rear half, and the good stuff remained on the workbench in front of me.




   The next task is to cut off the front output. I bolted the adapter plate to what was left of the NP231 and began cutting with a hacksaw. The case was very easy to cut, and in a few minutes I was left with what was to become the Crawlerbox.

   Now that the output is gone, there is a hole left that must be sealed. I headed off to the local fabrication shop to have a 3/8" aluminum plate welded over the hole. A few hours and $20 later I had my Crawler back and ready to be installed.

   Next up is to bolt the rotation ring to the Dana 300. The rotation ring is used to set the clock the transfer case to the desired angle. The adapter plate is then bolted to the clocking ring at the appropriate angle for your installation.



   There are 2 more steps before installing the crawler. First is to shorten the shift rod. I needed to shorten the rod to 7 1/8", the chop saw and grinder made short work of the task and I was ready to move on. Next on the list is setting the endplay of the mainshaft. This is accomplished by installing a shim and test fitting the Dana 300 & adapter plate to the Crawlerbox. You add shims to the mainshaft until their is a gap between the plate and the Crawlerbox. Then remove one shim and you are good to go. With the endplay set, I was ready to install the crawler. With plenty of RTV to seal the adapter, I bolted the 231 to the adapter plate.

   The Crawlerbox is installed into the Jeep just like the NP231 that it once was. Simply bolted to the transmission. Though the stock transmission mount is still used, Mad Rooster recommends adding a support to crawler adapter to help support the extra weight. I simply welded a mount to the adapter plate and bolted it to the skidplate with a bushing. I also notched the skid plate to clear the Dana 300.

   In a Wrangler, the stock shift linkage can be hooked up to the crawlerbox. If you don't have that option, a simple shift linkage can be fabricated.

Contact
Mad Rooster Off-Road
Phil Porter
Madera, CA
559-232-5566
madroosterfab@yahoo.com

[Jeffy]

Ok, I moved this to tech since I wanted to compare this to doing a Klune V.  How about using two 2.72:1 boxes.  It would give the me 2.72:1 2Lo or 2.72:1 4Lo while also giving me 5.44:1 compound 4lo.  Overall ratio for me with 4.56's would be around 136:1.  Think that's low enough?

What about strength?  I'm not sure how the lever would be handled.  Squeeze two sticks though the floor might be interesting.

[FourbangerYJ]

Ok, I moved this to tech since I wanted to compare this to doing a Klune V.  How about using two 2.72:1 boxes.  It would give the me 2.72:1 2Lo or 2.72:1 4Lo while also giving me 5.44:1 compound 4lo.  Overall ratio for me with 4.56's would be around 136:1.  Think that's low enough?

What about strength?  I'm not sure how the lever would be handled.  Squeeze two sticks though the floor might be interesting.

You could do alot with 136:1. But your choices are more limited by having both 231's 2:72. You would be amazed how much you use 4:1 if you had a Klune. I would depend on the type of wheeling you do. There is a big hole between 5:44 and 2.72. You could add a 4:1 in one of them but that would not be cost effective at all.

Strenth...HMMmm I would think it would be strong enough. My buddy runs a Klune 4:1 infront of his 231 and everything has held up for nearly 3 years with some hard wheeling.

I think for the money and a easier install I would do the Klune. But then I am pretty biased

[Jeffy]

Well, there are times when I'd probably use 2.72:1 like on the Rubicon between obsticals.  4:1 is way too low for driving the whole trail.  Not to mention once at the top of Cadillac hill, it's dirt fire roads.

I should be doing fine with anything above 100:1.  I'm sticking with 35's for sure.  With two 2.72 boxes, I'd esentually have 4Lo and 2Lo without having to get a 2Lo kit.  I wouldn't buy a Klune 2.72:1 though.  Seems a waste.  If I got the 4:1 Klune and kept the 2.72:1, I'd have less overlap.

Too bad, I didn't know about the kit before though, I once had a spare AX-5 and a 231 just sitting around.

I think what it comes down to is; would I never use a compound low or not?   I'm going to stick with Left Coast trails.  Some small trails, the Rubicon and surrounding trails.  Maybe Johnson Valley.  Nothing too hard core though. :wink:

[FourbangerYJ]

That setup would work.
Given a choice I would rather have 2.72, 4, 10.88. VS. 2.72, 2.72, 5.44.
You said you wanted to do it for cheap. This is a good way to do it.

You would be surprised how much you use compound low. It's kinda like growing a 3rd arm....you always want to use it.

I am a west coast guy for sure! I have not done the 'Con yet. We always end up doing the Dusy. It's closer and waaay less crowded. There are some good trails in that area. Outside Fresno about an hour or so.

If you are down this way and want to go to JV let me know in advance. I would love to run with you. I am no expert out there but know a few of the trails. There are a couple of trails that are not crazy hard.

[Jeffy]

Well, would I need 10.88:1 in JV or Dusy?  I'm not sure if I'd be doing any of those trails anytime soon but I'd like to.  

The Rubicon's only rated a 3.5 if you decide to do Old Sluice and Lil Sluice.  The trail is doable with 2.72:1 and some decent tires.  Lower gears would be better though.  But 10.88 wouldn't be required.

[FourbangerYJ]

Well, would I need 10.88:1 in JV or Dusy?  I'm not sure if I'd be doing any of those trails anytime soon but I'd like to.  

The Rubicon's only rated a 3.5 if you decide to do Old Sluice and Lil Sluice.  The trail is doable with 2.72:1 and some decent tires.  Lower gears would be better though.  But 10.88 wouldn't be required.

  There is miles and miles of 2WD prerunner roads. But all the trails require lots of gearing for the stick shift crowd. Once at the trailhead I put it in Lo-Lo and use the tranny to change the ratio's.There is some pretty big sand dunes as well. I need alot more HP for the dunes. You could do some of the trails with just 4:1 but more gearing is better. I would say 100:1-200:1 for the 2.5L would be good.

Dusy: the first couple of years I ran it with the 231 with 4:1. It was fine. Last time was the first time with the Klune. I liked it much better. There was a guy in a XJ I-6 about 42:1 with us last year. I don't know how he did it. He did not have much fun. I tried to stay in the bronco case only in the easier stuff.  I can't imagine doing it without 4:1 or lower.  It did not take much rough stuff to want to run just the Klune. Most of the trail was done in 4:1. There was a couple of stretches that I put it in Lo-Lo first.  There is no bypasses. I really like that trail.

[Jeffy]

I'm figuring 150-200 would be above average for a 2.5L on West trails. My current gearing is 49:1.  I know that's not low enough to feel comfortable with on trails over 3.5.  Too much wheel spin for the moderatly difficult stuff.  Even for a 3 trail, it will work but require more work.  I don't plan on doing dunes since the bowls can be big and the 2.5L isn't cut out for high HP to get out of them.  But the lighter stuff, 2.72 would come in handy.  Especially, 4WD on-road if I want to head up into the Sierra's.  That's one of the reason's why I want to keep 2.72 and not go with a Tera.  There are some winding roads locally where 4Hi might come in handy also.

Tough decision though.

[FourbangerYJ]

I was seriously considering the SM420 tranny with a 7.05 first with the 231. Would have been around 138:1. Then my friend got his Klune and I knew that there was no way I would be happy without one.
With the 4:1 I was fairly happy. But there was alot of time I was to low, or not low enough.
With a 2 box setup you can usually find a gear that will work for the trail or section of trail.

2.72, 2.72, 5.44 is not a bad set up. It would be the cheapest way that I can think of to get 2 boxes. The nice thing is you could add a 4:1 later on and get the 2.72, 4, 10.88 if you felt you need it. But I would think that you would be happy with a pair of 2.72's. You would still have the best of both worlds. You could do all level of trails

I can't imagine having a 5.0 or a 6.0 Atlas UNLESS alls I ran was the Hammers. Gotta have choices.

:EDIT: Is 150:1 really needed?? Probably not but I have found that if you have it you will use it and the varity of trails you run will expand.

[Jeffy]

I too thought about a SM420 but I don't think I want to loose 5th gear.  If I was going to swap engines I'd to AX-15 or a NV3550, I think.  The NV4500 is way overkill and is too damn heavy.  I think I'm fine with my AX-5 though, it hasn't let me down.  I rev it up to 5000rpm then shift a lot too.  Honestly, for most trails 60-80:1 is probably a more respectiable range.  Although 100+: make thigns a lot easier.  Especially with a 2.5L.  I know Jason Bunch did pretty good with a 2.72:1 Klune and a 4.3:1 Atlas.  I think that's a really good setup.  I don't really plan on doing anything too hardcore so that's one of the reason why I'm thinking about sticking with something below 180:1 range.

I think price is a big factor.  I don't drive my Jeep offroad as much as I used to and at that point, I was only taking it offroad every few weeks on light to moderate trails.  Nothing over a 2.5.  For some reason, I'm getting a bit tired of my Jeep since it's used as a Daily Driver.  :shock:  I've built it to the point where it it's fun for the short trip or even an occasional long trip (had several 300-700 mile road trips).  It gets tiring when you have to be somewhere on time and want to be comfortable.  I need something else, LOL!

I've got a lot of ideas on what I want, but can't afford that much down time right now.  Although, I do have a garage.

[Jeffy]

Thought about this some more and decided that an Atlas would be a better option then this doubler crawler 231 idea.  You'd get 2Lo, along with 4Lo but without having the whole drivetrain extend 7".  I'm wonder with the new Atlas, will the 4.3's and 5.0's drop in price.  Still not sure if I want the Klune V/231 or just go with an Atlas.  Although the Stak would be nice too but not for $3K.

[FourbangerYJ]

An Atlas is a great T-case. Not sure if the prices will drop or not.
The best thing to do is ask yourself if you can stand to drive the trails that you like to do or would like to do with just 4.3:1 or 5:1. To low, to high, etc.
The Klune-231 is a OUTSTANDING setup. If you can move the motor forward yourself along with the other install stuff it would be cheaper than just an Atlas. I would guess around 2K for Klune and SYE. Moving the motor forward 6 inches and you could use your currant front D-shaft. Saves you a few bucks. Atlas would require D-shaft mods for front and rear.

[Jeffy]

Decided to throw some numbers down.  I noticed I screwed up on the Doublers compound low. It's not 5.44:1 but 7.38:1.

Atlas II 3.8:1 Transfer Case   $1899.95
Atlas II 4.3:1 Transfer Case   $2189.95
Atlas II 5.0:1 Transfer Case   $2389.95
Atlas II 6.0:1 Transfer Case   $2454.95

NVG241-OR 'RockTrac'  4:1 Transfer Case   $2359.95

TeraFlex 4to1 4:1   $829.95
Super Slim SYE   $299
(Optional: Wide Chain   $325)
(Optional: 2Lo Kit   $199)

-----------------------------------
Total   $1128.95 (1652.95)

Klune V Underdrive 2.7 or 4:1   $1750
Super Slim SYE   $299
(Optional: Wide Chain   $325)
(Optional: 2Lo Kit   $199)
-----------------------------------
Total   $2049 ($2573)   2.72:1/7.34:1 or 2.72:1/4.0:1/10.88:1

NV231-J Doubler Kit   $??? ($500)
Welding Aluminum $20
NV231 Transfer Case 2.72:1   $300-500
Super Slim SYE   $299
(Optional: Wide Chain   $325)
-----------------------------------
Total   $1119-1319 ($1444-1644)   2.72:1/7.39:1

[FourbangerYJ]

Looks like the prices of the Atlas's have come down a bit. I think looking at the data I would still do the Klune/231. I wouldn't do the wide chain. 2lo I had it and liked it alot. I have a Detroit in the front. You would have the case apart to do the SYE anyway. They can be had for around $150 IIRC. But it would depend on your choice for a front locker.

For about the same money spent you would get alot more for your money. But it's alot more work to get it in, but it is well worth it.
You may never use the compound low for the type of trails you run. But I know for fact that you would use just the 4:1 or the 2.7:1 everytime you get out. To me that is worth every dime and busted knuckle putting it in.

I would never do the 2.7 X 2.7. That would suck unless all you did was the real rough stuff or the real easy stuff.

[Jeffy]

The only problem I have is I don't have access to a welder or someone who can weld right now.  If that was the case, I would consider moving my whole ending forward a few inches.  That would involve punching some new holes into the frame to reuse the stock skid, too.

I think the advantage of the 231 doubler is that it's cheap and gives you 2lo automatically. It would give you three speeds though.

The next cheapest is the 4to1.  Downside is it's only a 2speed.

Then we have the Klune V.  The 2.7 and the 4.0 seem to be priced the same.    I'd want to add $50-100 extra for the 23 spline input shaft though.  Do you have the the shifter or cable?  I'm not sure if I'd bother with the 2Lo or not.  I guess it would be a good time to do it though.  The only other problem with the SS SYE is that I'll have to figure out how to recalibrate the speedometer.

RockLoc would be a nice option if it wasn't so expensive.  I'm not sure if there is a 21 spline input shaft for it either.

As for the Atlas, I wouldn't bother with anything less then 4.3:1.  5.0 or 6.0 would be nice though.

Looks like a Klune V 4:1 is be best choice though.  Now if I could move my engine forward, I wouldn't have to get the SS SYE or a SYE for that matter.  Although Klune recommends a HD SYE.