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t-case doubler questions

Old 09-18-2012, 06:11 PM
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Default t-case doubler questions

im looking to toss a t-case doubler at my cherokee. in my daily driver i have a np245 (with part and full time) in my parts truck i have a np231.. i also have a 95 dodge ram thats unroad worthy siting around, dnt know what it has but either another np231,np231hd or a np241.

iv heard theres a kit thats for a np231/231 mate, would this work on a np231hd the same?

i have a 3" rough country short arm kit for the truck 2, with added lenghth to the t-case would it be ok to run stock driveshaft until it breaks (because of extra t-case lenghth mabey it wont fall out at full articulation?)?
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Old 09-18-2012, 07:23 PM
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Okay well I've never heard of a 245? And you don't have to worry about a drive shaft falling out at 3". Just curious, why the want for a twin stick?
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Old 09-18-2012, 07:24 PM
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And if you insist on it, I would look for a d300.
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Old 09-18-2012, 08:35 PM
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Originally Posted by BNJeepsta View Post
Okay well I've never heard of a 245? And you don't have to worry about a drive shaft falling out at 3". Just curious, why the want for a twin stick?
oops didnt see that, typo np242
i want to have it drive as close to stock as possible on the road.
iv got the d44 tow package with 3.54:1 gears that i want to leave. iv got an AX15 trany to swap in, i want to possibly lower the first and second gear slightly to compensate for tires and deffinetly make the fifth an overdrive, im also considering aftermarket torque converter to compensate for tires on road and add power(torque) on and off road.


with that, i want the double stick to drop it way down when i need to offroad, all this because i want to avoid regearing my diffs for cost and fuel economy but have a heavyduty offroad gear also
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Old 09-18-2012, 08:42 PM
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Originally Posted by BNJeepsta View Post
And if you insist on it, I would look for a d300.
iv heard of the Dana 300 but dont know enough about it(its cast iron, has 2.62:1 as low range and its been used in more than a few ttc trucks is the extent of my knowledge) i also know its a more expensive opption. i know its not even close to the strongest but iv heard of enough ppl running modifyed np231's, iv also got the three t-cases already and i would like to be 1 less lying around as well, if i hv it i might as well use it.
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Old 09-18-2012, 11:19 PM
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First. You can adapt anything to anything with enough time and resources. That being said, the kits that I have made, like most manufacturers will bolt almost any round 6 bolt pattern case to the back of the front half of a 231J.

At first I thought all 231 t cases had the same bolt pattern and outside profile, just different internals. I was wrong.

A little case info for you.
- A 231J comes in 2 different spline counts. pre 91 = 21 spline. 91 and later = 23 spline. Both have the same casing and most inner parts if not all are interchangeable.

- A 242J also comes in 2 spline counts same as above. The casing is different and can not be used as a front case because the adapter will not bolt to it. It can be used as a rear case though as it has the same 6 round bolt pattern. The internals can not be swapped with a 231.

- The 231C I pulled out of a chevy blazer with a 4.3 was 26 spline like most have indicated. It has a 6 gear planetary. Also has the wider chain and drive gears. The casing is different, much bulkier and the holes will not line up on a standard 231 adapter plate. because of this it cant be used as a front case with a standard 231 adapter kit. Also, the mounting bolt pattern was not 6 bolt round, it was only 5! Because of this, it can not be used as a rear case. What you CAN do is switch all the internals into a 231J case for a better built 231 with 26 spline input, 6 gear plantetary, and wide chain.

- The D300 is a more expensive option but has its perks. because of its cast contruction it can only be used as a rear case. It does have the round 6 bolt pattern though so this is ideal. It is not chain driven and therefor deemed stronger. You dont have to buy a SYE because it already has a fixed yoke, so you have saved 180 dollars there. It is also possible to twin stick the D300 itself, that way you can have rear high, rear low, front high, front low, 4 high, and 4 low. On top of that you would have low low as an option too when combined with a doubler. Dont forget this case will need to be flipped as it comes passenger drive drop stock.

- 231HD. To be completely honest I dont know a bunch about these. Use the previous information to inspect the case and decide what it can be used for.

Dont forget that each case has different spline count and input shaft length possiblities. Make sure you choose a manufacturer that custom makes each shaft for each possiblity.

Hope this was helpful.
Kris

Last edited by Lead Foot; 09-18-2012 at 11:23 PM.
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Old 09-18-2012, 11:57 PM
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Originally Posted by Lead Foot View Post
First. You can adapt anything to anything with enough time and resources. That being said, the kits that I have made, like most manufacturers will bolt almost any round 6 bolt pattern case to the back of the front half of a 231J.

At first I thought all 231 t cases had the same bolt pattern and outside profile, just different internals. I was wrong.

A little case info for you.
- A 231J comes in 2 different spline counts. pre 91 = 21 spline. 91 and later = 23 spline. Both have the same casing and most inner parts if not all are interchangeable.

- A 242J also comes in 2 spline counts same as above. The casing is different and can not be used as a front case because the adapter will not bolt to it. It can be used as a rear case though as it has the same 6 round bolt pattern. The internals can not be swapped with a 231.


- The 231C I pulled out of a chevy blazer with a 4.3 was 26 spline like most have indicated. It has a 6 gear planetary. Also has the wider chain and drive gears. The casing is different, much bulkier and the holes will not line up on a standard 231 adapter plate. because of this it cant be used as a front case with a standard 231 adapter kit. Also, the mounting bolt pattern was not 6 bolt round, it was only 5! Because of this, it can not be used as a rear case. What you CAN do is switch all the internals into a 231J case for a better built 231 with 26 spline input, 6 gear plantetary, and wide chain.

- The D300 is a more expensive option but has its perks. because of its cast contruction it can only be used as a rear case. It does have the round 6 bolt pattern though so this is ideal. It is not chain driven and therefor deemed stronger. You dont have to buy a SYE because it already has a fixed yoke, so you have saved 180 dollars there. It is also possible to twin stick the D300 itself, that way you can have rear high, rear low, front high, front low, 4 high, and 4 low. On top of that you would have low low as an option too when combined with a doubler. Dont forget this case will need to be flipped as it comes passenger drive drop stock.

- 231HD. To be completely honest I dont know a bunch about these. Use the previous information to inspect the case and decide what it can be used for.

Dont forget that each case has different spline count and input shaft length possiblities. Make sure you choose a manufacturer that custom makes each shaft for each possiblity.

Hope this was helpful.
Kris

yes this is massivly helpfull
in interest what adapters have you made?


my big problem is i have no idea who makes adapters,name brands or backyard mechanics i have no idea?
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Old 09-19-2012, 12:10 AM
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231J to any case with 6 round bolt pattern. 21, 23, and 26 spline.

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Old 09-19-2012, 03:40 PM
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may sound like simple questions but asking cause i dont know or not sure

- the 6 bolt pattern is where the 2 halfs of a t-case are connected front and back, or where the t-case meets the trany?
-is the adaptor plate all thats needed for a 6 bolt to anothter 6 bol swap, is there other hardware needed, can i use existing nuts and bolts from either case?
- do different or the same model of cases from the same mobel of vehicle usualy have the same bolt pattern? aka my 242 and 231?
-the np242 has part time and full time 4h, does this present any space issue?
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Old 09-19-2012, 04:01 PM
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I try to think no such thing as a stupid question but sometimes it happens. lol I dont think any of your questions are stupid though.


The ROUND 6 bolt pattern is pattern on the front of the case that bolts to the trans. The front case needs to have this pattern to bolt to the back of the AW4, AX5, and AX15 trans. The rear case also needs to have this bolt pattern to bolt to the back of the front case half (to the adapter that comes with a doubler kit.)

Kits will usually come with the adapter plate that bolts to the back of the front half of the the front case. A weld in block off plate to fill the hole created when the front output shaft section is cut off of the front case. The clocking ring that allows you to clock your rear case 180 degrees in increments of 7 degrees. A "spud shaft" or front case main shaft that connects the front case planetary to the rear case input shaft. And finally clocking ring and adapter hardware. (bolts and such) B

esides that you will need necessary tools to remove and install the cases, a band saw or sawsall to cut off the front output section of the front case, means to weld aluminum to weld in the block off plate, RTV to seal everything back up, and alot of ATF to fill the cases. Dont forget it is suggested that you run a second crossmember to support the rear case and handle the excessive torque. You will also need to figure out a shifter arrangement for the rear case. There are lots of write ups on this.

I also supply 2 clocking ring gaskets with my kits so there isnt any sealing issues that can occur sometimes when using RTV and lock tite between the clocking ring to the adapter plate. I also will be planning on releasing a crossmember and shifter setup to purchase seperate of my kits. Welding would be required for those products.

As far as I know, all 231J and 242J t cases have the same 6 round bolt pattern.

The 242 case is bulkier and hangs .75-1" lower then a 231. If you arent worried about the low hanging t case then this isnt an issue. The strength of the internals that allow full time operation are also in question but many people run this case with no problems.
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Old 09-19-2012, 07:36 PM
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not to be a guy who picks on details. but i could have swore you said you had an ax15. and wanted lower ratios. then later in your post mentioned an aftermarket converter? for a standard shift trans? am i missing something here? do you mean an aftermarket clutch? torque converters are an automatic part not standard shift...
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Old 09-19-2012, 07:38 PM
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Originally Posted by liqour crazy View Post
not to be a guy who picks on details. but i could have swore you said you had an ax15. and wanted lower ratios. then later in your post mentioned an aftermarket converter? for a standard shift trans? am i missing something here? do you mean an aftermarket clutch? torque converters are an automatic part not standard shift...
I missed that. lol Curious what the answer is too...
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Old 09-19-2012, 07:39 PM
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Originally Posted by Lead Foot

I missed that. lol Curious what the answer is too...
I'm pretty sure he said an ax15 to swap in
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Old 09-19-2012, 07:40 PM
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Oh and a lot of dirt track cars have a manual tranny with a torque converter. May not apply to jeeps but it does exist
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Old 09-19-2012, 08:05 PM
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thanks lead foot this is greatly helpful. my plans are to start this project 2 or 3 mounths into the new year but if i have any more questions i will brin this thread back.

powertrain, engine and electrical are my main weaknesses, yes i did say torque converter, and it was a boo boo, im still new to this and admittidly made a mistake, derp

clutch kit is on the list though
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