Homebrew crawler box (my typical long wordy explanation)

Now that our relocation has pretty much fallen into place and I have a new job and can afford to play with the green XJ again, I'm considering making a home brew crawler box similar to the one described on bc4x4.com using 231 low range parts. Now, shortly before I moved, I spent some time & money building up my existing 231 with an AA SYE and Tera 2-low; but I'm thinking that perhaps it will still be the weak link behind an additional 2.72:1 reduction. So my plan is this... use either an early Bronco Dana 20 or Ford NP205 behind the 231 crawler box and save my built 231 for another project. So, anyone have any input as to which would be better in this appliation? I tend to build beefy enough for the way I handle my rig, which doesn't necessarily mean the ultimate in huge heavy duty parts; I tend to upgrade from stock to something adequately strong that isn't overly massive or expensive, which is why I wouldn't consider an Atlas or NV241OR. So, any opinions on Dana 20 versus NP 205? I'm leaning towards the Dana 20 due to its smaller size and weight, both being gear driven in a cast iron case.

I know you've dumped some dough into the 231 with your upgrades, but what is your reason for doubling up a gear driven HD case like a 205 with a weak chain driven 231?

I think if your into doubling you should go 203/205 & call it good.

2cents.

-jb

How's it going mark? I would try going with the 20 just becasue that's the one I actually know a little about. one thing with the 20 (at least the bronco 20) is it has the tex pattern (5 studs instead of 6 like the 231). I'm guessing these are going to be divorced as well. I can't really see mating the 20 to the 231 without some radical machine work.

One thing to look into is making a crawler box out of your 231(instead of a 241 like in bc4x4), and finding a NV241 and getting a SYE for it. This isn't bad since you're putting the weaker(231) in the front of the set-up. A few months ago I bought a np241 to make a crawler box....but then I noticed it was brand new, and the HD version, so I just sold it to make some money . The HD version is massive and won't break for anything, however, you HAVE to keep the slip-yoke, there is no conversion for the HD version, only the 241 light duty can be converted, so if you are getting a 241, i woudl advise against the HD version. The 241 has 6 planetary gears compared to the 3 or 4 (I forget) the 231 has, and a much larger output shaft.

ORRR, you can make a crawler box out of the 231 or 241 just like bc4x4, doing the through studs to keep the same 6 stud pattern, buy an adapter at high impact gear, and run the dana 20 behind that, and be set with about a 6.5:1 with both in low.

The 205/203 is nice because you have a variety or gears, and is almost bullet proof, but you're not getting any more than 4:1 with both cases in low(IIRC they are both 2:1 low range) and they are massively heavy. I would never do that set-up unless I was running humongo tires and one ton drive train all around. Just my opinion.

Hope you liked the long response marky. _nicko_

NP205 is a 1.98:1 low, and the 203 is, i believe, a 2.63, or 2.54 or something like that. Comes out to about 5:1ish. IMHO, the big iron cases are just that - big and iron. Bulk and weight aren't such a good thing. Unless you have a super happy throttle foot or a very built XJ motor, I'd just put a 4:1 planetary in the 231. Or build up a flipped Dana 300 if you need even more strength.

Are you just excited about having more low range gear options? The XJ could really do without the shorter rear driveshaft caused by an extra crawl box. I'd avoid it.

Jared

XJ rear driveshaft is plenty long. I would not worry about that whatsoever. More gearing options (within reason) in my opinion, is a good thing...not just a cool and exciting thing. No one needs a 10:1 crawler box or anything. But my jeep, 4:1 t-case, ax-15, 4.56, and 33's, I feel a lot of the time I should be going slower. If I had a 2:1 or a even a 1.5:1 in front of my t-case, I'm sure I would be much happier. _nicko_

Wouldn't it be cheaper to get a Klune V or Axis underdrive? Then you'll have 6 gears & low low gears.

-jb

A 203 provides a reduction of 2:1.

I see I wasn't absolutely clear in my initial post, seeing how it was interpreted so many ways.

I've decided to go with the Bronco Dana 20, a pre-'73 model with the T-style shifter. It will be easy to adapt to a Jeep shifter, and have 2.46 low range. I'll use the 2.72 low range gears and a modified main shaft from a broken 231 in front of it in a custom housing a-la BC4x4. I will then have a reasonably sized, gear driven, iron housed T-case with a small lightweight crawler box married to the front of it, giving me the following options: 1:1 2wd or 4wd, 2.72:1 2wd or 4wd, 2.46:1 4wd, and 6.69:1 4wd. The greatest part of this is that a Bronco Dana 20 can be had for ~$150, and the rest of the work comes from me. And I still have the built 231 to keep for another project or sell. Compare that to the hefty price tag for an Atlas, Klune, Tera Low, or 241OR.

I don't want to put any more money into my current 231, and if I put a crawler box in front of it, it certainly won't last. I feel that the single 2.72 reduction will be inadequate with 35's and 4.56 gears, having only moved the truck around in its current built state in parking lots and onto trailers for the recent move.

I'm not concerned about driveline length, there is planty of room compared to a swb jeep, and I want to avoid the huge weight of the 203/205.

That should be good, but I definitely would recommend using a 241 for your crawler box rather than a 231. You can find the GM pass side drops pretty cheaply. That's what the guy on BC4x4 used. Keep track of how you're building it as well...don't forget anything. _nicko_

The crawler box won't see any more torque than a single 231 T-case since it is first behind the transmission... the transfer case is what needs the beef since it will see the added torque multiplication of the crawler box, hence the Dana 20. The BC4x4 article used a 241 for parts to beef up the 231 transfer case, and used 231 parts in the crawler box. I have Peterbilt's old 231 front case half and my old 231 main shaft to use in the crawler box, and I'm getting a '72 Bronco Dana 20 for $100. Can't beat that in the bang-for-buck department, IMHO.

ahhh..didn't know he used the 241 planetaries in the 231....that's a better idea. I was looking at a klune-v to dana 20 set-up myself earlier this year, but noticed it was way out of my price range, and I had more important stuff to spend money on. This will be just as good if not better when you factor in the price you're paying. Have fun with it, and I can't wait to see how it comes out.

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