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NP231 doubler / crawlbox

Wildman

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Why is this, and is it the same for manuals and autos? Not sure if the different gear options make a difference. And am I off my rocker here? On paper I could build a 231/231 doubler for less than finding or building a single 4:1 tcase, but is that more trouble than it's worth?

From what I have found there is only maybe one company still making the crawler box kits. Where 15 years ago there was like 6-10 companies that offered a kit to convert the 231. Unless you have a LJ I think the length of a 231/231 would be too long.
This is why what Gollywomper did is the better option.
 
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LincolnJr

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From what I have found there is only maybe one company still making the crawler box kits. Where 15 years ago there was like 6-10 companies that offered a kit to convert the 231. Unless you have a LJ I think the length of a 231/231 would be too long.
This is why what Gollywomper did is the better option.
Yes, I do have an LJ. I'd have to figure out what the final length would be 231 + half-ish 231 - SSYE...
 
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LincolnJr

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If the 231 crawler box is close to 5” long you may want to look at NWF Ecobox.
Thought about that one too. $1000 for the box and then:
Additional Parts Required:
NP231/NP241 Input Shaft to match your Transmission
Planetary Gear Assembly From NP231/NP241 (6 pinion recommended)
Annulus Gear
Input Bearing From 231/241 (Matched to Input Shaft)
Shift Range collar From Manual shift NP231/NP241
Input Bearing Retainer w/ Seal from NP231/NP241
6 pinion planet is about $250, and I'm not sure how much of the other stuff I could get from a spare NP231. Would also need a shifter (cable shifter - $170). $1600-1700ish total. Would be a much cleaner setup I think.
 

RustyAutoholicGuy

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The NWF Ecobox is 8" long:

5J2310g.png
 

Gollywomper

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Thought about that one too. $1000 for the box and then:

6 pinion planet is about $250, and I'm not sure how much of the other stuff I could get from a spare NP231. Would also need a shifter (cable shifter - $170). $1600-1700ish total. Would be a much cleaner setup I think.
Ya I’m not sure they make the super short box that bolts to a 231 either.
 

Wildman

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Yes, I do have an LJ. I'd have to figure out what the final length would be 231 + half-ish 231 - SSYE...

If you go over on Pirate and look thru some of their doubler threads I'm sure you can find the total length. Have you found a company who is still making the kit?


OK I found one person making the doubler and he's even close to me, in Yakima.


Here is the length of the cut 231 so just add that to your stock 231 with SYE.

the 231J front half is 6 7/8", the block off plate is 1/2", and the clocking ring is 1/2", total length of 7 7/8"
 
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RustyAutoholicGuy

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If you go over on Pirate and look thru some of their doubler threads I'm sure you can find the total length. Have you found a company who is still making the kit?


OK I found one person making the doubler and he's even close to me, in Yakima.


Here is the length of the cut 231 so just add that to your stock 231 with SYE.
I have that kit but it's rough. I was going to originally do that but decided to go with the doubler kit. If someone wants the parts for the NP231 doubler I can get all the parts and I'll sell it for 50% of that price, I'll never use it but it's going to require some fab work on their end.

The eco box for the Dana replaces the 300s input shaft. The eco box i is right at 5”.

OH are you talking about the black unit? *EDIT* yup okay I'm getting caught up now on all the pages in this thread, I jumped in without knowing everything yet!
 
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Gollywomper

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I have that kit but it's rough. I was going to originally do that but decided to go with the doubler kit. If someone wants the parts for the NP231 doubler I can get all the parts and I'll sell it for 50% of that price, I'll never use it but it's going to require some fab work on their end.



OH are you talking about the black unit? *EDIT* yup okay I'm getting caught up now on all the pages in this thread, I jumped in without knowing everything yet!

This is what makes the 300 a great option. Together it puts total length at 17”.
However, as Blaine pointed out, you may run into front drive shaft issues on an auto trans rig because the 300 is narrower than a 231.
 
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Wildman

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I have that kit but it's rough. I was going to originally do that but decided to go with the doubler kit. If someone wants the parts for the NP231 doubler I can get all the parts and I'll sell it for 50% of that price, I'll never use it but it's going to require some fab work on their end.
Damn if I was JUST starting my build I would be all over this.

@LincolnJr you should JUMP on this.
 
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Blackjack

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That’s is pretty much what lead me to my decision. Is the 205 case wider to help get passed the trans?
205 even with an aluminum case makes an Atlas seem lightweight.
Sounds like another perfect option for the TJ.

Actually what I would like is the Dana 300 widened out another inch with a new 4-1 gear set built to be left hand drop. That is a case that makes sense for a normal TJ.
Was that not what the original Atlas was?
 
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Wildman

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Frog Fab also has the doubler boxes.


With the Novak short shaft and a doubler here is the total length.

omplete 231-d300 kit with novak supershort tail shaft on the d300 is 16.5inch total lenght

 
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Gollywomper

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Frog Fab also has the doubler boxes.


With the Novak short shaft and a doubler here is the total length.



What does it take to make the electronic speed sensor signal work with the TJ?
 

mrblaine

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What does it take to make the electronic speed sensor signal work with the TJ?
It is already electronic on the TJ. There are two types. Standard 231 uses a gear driven Hall Effect in the sender with changeable gears, 241 uses a tone ring and Hall Effect. Both can be adjusted with a digital correction box.
 

Gollywomper

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larger tires with stock gearing results is less fuel economy and worse overall drivability on and off road.

Larger tires with the appropriate gears to compensate getting close to stock ratio is better then the above regarding fuel economy and overall drivability on and off road.

The factory gears towards mpg’s not power.

Depending on your average top speed taller gears/higher ratio numerically can improve gas mileage and power.

If you wheel in high traction area’s lower gears are very helpful.

if you wheel in mud and loose dirt or sand it is not.

No matter what your reduction choice for your terrain regearing for your larger tires is step one.
What makes a double so great is you retain your stock low range gearing with options for lower gearing as needed.
It does not compensate for tire size. That should be done with gearing the axles.