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Anyone here ever here of double an np231 t-case? i have the np231 in my truck as well as another in my yard from an s-10 blazer.i also have access to an np208 and 205 case.
 

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No, The drivetrain isn't long enough to. If you really want to do it then I guess you could extend the rears axle by a foot or so and run dual Tcases. Have fun doing it though because it's not as common in jeeps as yotas so parts are going to be hard to come by.
 

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Look into a 231-Dana 300 Doubler. The unit will be shorter then your current setup, and you can put the 4:1 in the 300 for around 500 bucks. I plan on doing this once I set up some full width axle's.
 

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Discussion Starter #4
im considering just putting a 4:1 kit in the np231 but i figured see what kind of other options there are.the extra range is kind of attractive though
 

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Firstly, NP231s are garbage. Beyond throwing a HD SYE in them, and perhaps a 2low if you want it, they have no future. They simply have too many shortcomings in places that can't be upgraded. Yes, they can survive a lot of use, but that does not make them great. Using the planetaries from a NP231 as a doubler is not a bad idea, box4rocks and madrooster both offer them for $499. You also need to weld a small block-off plate in the remains of your NP231. It is aluminum, and you don't want it to leak, so it makes for a not-so DIY job for a lot of people.

The problem with either a 4:1 kit (teralow) or using a NP231 behind a doubler is that it can't handle the added torque. For a doubler, imagine going from your decent gas 6-cylinder torque output of 225ft-lbs to the world of modded diesels with 612ft-lbs of torque. Would you try running a NP231 behind a hopped-up cummins, or duramax? I hope not, because it wouldn't last, not even on the street.

(Before people bish and tell me a NP231 is rated for about 1600ft-lbs of input torque, remember the first gear ratio has to be factored in there, plus TC slip or clutch slip, and any allowance or tolerance for potential shock loading. We easily exceed this number in the above example if we run an AX-15 transmission.)

So, a NP231 behind a doubler is a bad idea. Low gears are also a bad idea, that input torque rating is with the assumption of 2.72:1 planetaries. The front output, chain, and perhaps the entire chaincase would be operating way beyond their designed limitations. I don't say rear output, because I'm going to assume you have a HD SYE.

So, we have other options for the rear of our double... The Dana 300 would be a good candidate (as previously mentioned), and a NP205 would only add a little more length to the over-all combination. Not that length is really a problem, an XJ rear driveshaft can lose a foot and the world won't end. The real problem with both these cases, at least IMHO, is the total price. But, I've argued the economics before... And I won't do it again. But it boils down to being CHEAPER in the end to buy an atlas or stak case (stak makes a mini-monster 3spd that would be pretty cool) and forget the whole doubler and having to upgrade a junkyard case (the case is the cheap part).
 

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No, The drivetrain isn't long enough to. If you really want to do it then I guess you could extend the rears axle by a foot or so and run dual Tcases. Have fun doing it though because it's not as common in jeeps as yotas so parts are going to be hard to come by.
check it out.......

Mr. Easy Web

SNORT4x4 forum - Np 231 doubler

there out ther dude...lookin into doin one myself
 

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The problem with either a 4:1 kit (teralow) or using a NP231 behind a doubler is that it can't handle the added torque.
Hmm, really? Tell that to all the guys out there running TeraLOWs or Klune-V/231 combos without problems. The 231 is no Atlas, or even D300, but it's certainly not garbage and it's certainly capable of running with a 4:1 gearset.
 

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Well it may not work for you but there seems to be others who it does work for.
 

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i have the NP231 with an advanced adapters SYE kit.. love it.. compact, light weight..

i also run a dana 30 AND a dana 35 on 35" tall tires.. i rock crawl the fawk out of my rig and have NEVER broken an axle..

point is its all it your diving style.. i use faness and manipulation to get through a line..
"when in doubt, throttle it out" absolutely not..
skinny pedal breaks shit..

ITS NOT THE RIG, ITS THE DRIVER
 

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This is Ames mister...
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Firstly, NP231s are garbage. Beyond throwing a HD SYE in them, and perhaps a 2low if you want it, they have no future. They simply have too many shortcomings in places that can't be upgraded. Yes, they can survive a lot of use, but that does not make them great. Using the planetaries from a NP231 as a doubler is not a bad idea, box4rocks and madrooster both offer them for $499. You also need to weld a small block-off plate in the remains of your NP231. It is aluminum, and you don't want it to leak, so it makes for a not-so DIY job for a lot of people.
I'm a little confused by this paragraph...are they junk, is throwing an SYE or 2LO in one a good idea, do they have a future or can't they be upgraded? Can they survive a lot of use? So using planetaries from a 231 is not a bad idea?

I think you need to make up your own mind before posting...

OP - as mentioned there are plenty of people running 231 doublers without issues (even behind V8's). There are some things that you can do to beef it up a little bit like a HDSYE, 6 pinion planetary gears out of a 241 or wider chain (some Chevy 231's and the NP207 found in early XJ's have 1.25" wide chain vs. the 231J's 1" wide chain.).

As far as wheel base goes you're ok there also. The 231/231 doubler combo adds about 7" (D&D's is 7 7/8" long) to your driveline and if you add an SYE at the same time you wouldn't gain that much length - it would depend on which SYE you went with but you might only add 1" of length. The rear DS would need to be shortened and you'd have to either buy a new front DS or have your current one lengthened because your front output would be upwards of 7" (or further) back than original.
 

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Discussion Starter #14
awesome that was the kind of information i was looking for. sounds like a pretty expensive endeavor though as oposed to jsut gettting a set of 4:1 gears.
 

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oooooo did not know that about the NP207 i pulled one of those out of an early XJ but thought nothing of it... is it worth anything?? better or worse than the 231??
 

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Not the biggest fan of the np231, has let me down....i switched to the NV241 already with 4:1gears, not the cheapest thing, but just throwing it out there.
 

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I'm a little confused by this paragraph...are they junk, is throwing an SYE or 2LO in one a good idea, do they have a future or can't they be upgraded? Can they survive a lot of use? So using planetaries from a 231 is not a bad idea?

I think you need to make up your own mind before posting...

Drink some Jet-B. I HAD made up my mind. For mild use, throw a HD SYE in it and a 2low if you're into that, and wheel it. BEYOND THAT THERE IS NO WORTHWHILE UPGRADES. If you want use it as a front case, FINE. The fucking planetaries DO NOT BREAK with the torque input they would see as a front case. As the rear case, you WILL BREAK A NP231 if you wheel in a non-pussy manner.

And before somebody gets all 'well, just pull your winch cable on all the hard stuff', THAT ISN'T WHEELING! See previous comment about Jet-B.

Thank you for understanding.
 

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Anyone here ever here of double an np231 t-case? i have the np231 in my truck as well as another in my yard from an s-10 blazer.i also have access to an np208 and 205 case.
T answer the original question, yes there is a way. Install a KLUNE V underdrive. It will bolt up and all you will have to change is drivelines (better put in a short SYE while your at it) and tcase linkage. but the question remains - is it practical? If you are looking to gain rock crawling gears and rock crawl, then you really would need to go to an Atlas and of course upgrade your axles. It is all going to cost money.
 

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This is Ames mister...
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oooooo did not know that about the NP207 i pulled one of those out of an early XJ but thought nothing of it... is it worth anything?? better or worse than the 231??
Definitely worse than the 231 because there are no SYE's made for it, the only good thing in that case is the wide chain...:thumbsup:
 
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