np231
CF Veteran
Joined: Apr 2008
Posts: 13,952
Likes: 17
Model: Cherokee
Get a wide chain and matching front output shaft from Dodge NP231D t-case, and wide main gear from a Chevy 231C .
Remove the 3 planetary low range and build a 6 planetary low range. If your low range gear doesn't have the 3 extra holes for the planetary gears, grab one from a chevy NP231C.
I recently learned that the 6 planetary from a Chevy NP241C is a drop-in for the NP231J as well.
Here's how I built mine:
Remove the 3 planetary low range and build a 6 planetary low range. If your low range gear doesn't have the 3 extra holes for the planetary gears, grab one from a chevy NP231C.
I recently learned that the 6 planetary from a Chevy NP241C is a drop-in for the NP231J as well.
Here's how I built mine:
Remove the snap-ring that retains the input shaft. Carefull! The input shaft and low range gear will fallout as soon as the snap-ring is removed.
Remove the large lock-ring in the low range housing in order to remove the input shaft.
At this point I had to use the pin and planetary gear as a makeshift jig so I could reinstall the two rows of needle bearings in the planetary. The two rows are seperated by a small washer.
After installing the planetary gears into the low range housing, use a cold chisel to stake the pins in place. Now you've got your own homebrew booty fab 6 planetary low range gear!
[IMG]http://i55.photobucket.com/albums/g138/FrankZ_2006/Vortec/IMG_3951.jpg[img]
Comparison pic of the OEM Chevy 32 spline main shaft and the JB Conversions short main shaft.
Remove the snap ring that retains the drive sprocket and the mode hub. Slip them off the the old shaft and onto the new short shaft.
Reinstall the input shaft into the lowrange, and then install those into the forward case half followed by the snap ring.
Re-install the mode fork, range fork, and the rail, followed by the front output shaft, chain and main shaft.
Re-install the magnet.
Don't forget that the oil pump goes on the outside of the rear half.
Hopefully you've been using a brass wire wheel in a drill to clean all of the mating surfaces. DO NOT USE STEEL WIRE WHEEL!!
Once your surfaces are clean it's time to add a little gasket maker. I strongly recommend.....
Re-assemble the two case halves.
Remove the large lock-ring in the low range housing in order to remove the input shaft.
At this point I had to use the pin and planetary gear as a makeshift jig so I could reinstall the two rows of needle bearings in the planetary. The two rows are seperated by a small washer.
After installing the planetary gears into the low range housing, use a cold chisel to stake the pins in place. Now you've got your own homebrew booty fab 6 planetary low range gear!
[IMG]http://i55.photobucket.com/albums/g138/FrankZ_2006/Vortec/IMG_3951.jpg[img]
Comparison pic of the OEM Chevy 32 spline main shaft and the JB Conversions short main shaft.
Remove the snap ring that retains the drive sprocket and the mode hub. Slip them off the the old shaft and onto the new short shaft.
Reinstall the input shaft into the lowrange, and then install those into the forward case half followed by the snap ring.
Re-install the mode fork, range fork, and the rail, followed by the front output shaft, chain and main shaft.
Re-install the magnet.
Don't forget that the oil pump goes on the outside of the rear half.
Hopefully you've been using a brass wire wheel in a drill to clean all of the mating surfaces. DO NOT USE STEEL WIRE WHEEL!!
Once your surfaces are clean it's time to add a little gasket maker. I strongly recommend.....
Re-assemble the two case halves.
Last edited by SeriousOffroad; Feb 20, 2010 at 08:59 AM.
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CF Veteran
Joined: Apr 2008
Posts: 13,952
Likes: 17
Model: Cherokee
True, but the Atlas t-case is still a replacement.
The OP asked about beefing up a 231J, which can be done very inexpensively using common parts that are easily obtained from just about any JY.
A little search via Google reveals that a 3 planetary is rated for 600 Ft Lb of Torque and the 6 planetary is rated at 1400 Ft lb of torque. Thats a huge increase in strength for a minimal investment.
For comparison purposes only:
A TeraFlex 4 to 1 kit replaces the front half of a 231J case and uses a 6 planetary low range.
Cost is $1000-$1200
A RockTrack NP241OR (Rubicon) T-case used is going to be pricey as well. I looked at a few and found out all of the used ones are made out of gold, platinum, and unobtainium. These t-cases also use a 6 planetary low range. Be careful buying a used one though. Stretched chains seem to be rather common and a new replacement is going to set you back around $300.
Cost $850-$1700
Atlas T-cases are the shizz! Truly a solid upgrade for those that need the beef, but the simple fact is that most of us don't need that kind of strength and features of an Atlas T-case.
Cost $2000-$2300, not including shifters, linkage, brackets, etc.
The cost beefing up an OEM NP231J with easily obtainable JY parts is going to vary by area, obviously some JY's are more expensive than others. My local JY gets $75 for a complete t-case, any flavor. Tear it down in the yard and the price for the individual parts needed is a lot less.
Estimated Cost for beefing up a 231J?
$50-$200
The OP asked about beefing up a 231J, which can be done very inexpensively using common parts that are easily obtained from just about any JY.
A little search via Google reveals that a 3 planetary is rated for 600 Ft Lb of Torque and the 6 planetary is rated at 1400 Ft lb of torque. Thats a huge increase in strength for a minimal investment.
For comparison purposes only:
A TeraFlex 4 to 1 kit replaces the front half of a 231J case and uses a 6 planetary low range.
Cost is $1000-$1200
A RockTrack NP241OR (Rubicon) T-case used is going to be pricey as well. I looked at a few and found out all of the used ones are made out of gold, platinum, and unobtainium. These t-cases also use a 6 planetary low range. Be careful buying a used one though. Stretched chains seem to be rather common and a new replacement is going to set you back around $300.
Cost $850-$1700
Atlas T-cases are the shizz! Truly a solid upgrade for those that need the beef, but the simple fact is that most of us don't need that kind of strength and features of an Atlas T-case.
Cost $2000-$2300, not including shifters, linkage, brackets, etc.
The cost beefing up an OEM NP231J with easily obtainable JY parts is going to vary by area, obviously some JY's are more expensive than others. My local JY gets $75 for a complete t-case, any flavor. Tear it down in the yard and the price for the individual parts needed is a lot less.
Estimated Cost for beefing up a 231J?
$50-$200
CF Veteran
Joined: Jan 2010
Posts: 2,059
Likes: 1
From: Indianola IOWA
Year: 1992
Model: Cherokee
Engine: 4.0
Think i am going to try to beef a 231 to replace my 242. can you tell me what vehicles i can source the other t-case parts from?
Last edited by posjeepxj; May 12, 2010 at 08:12 PM.
CF Veteran
Joined: Apr 2008
Posts: 13,952
Likes: 17
Model: Cherokee
Any Chevy 231 will have the wide chain and main gear. Mid-90's and up Dodge 231 transfercases also have the wide chain, and it will have the wide gear front output that will accept your front output yoke (np231J & np242J use the same yoke).
CF Veteran
Joined: Nov 2008
Posts: 7,874
Likes: 100
From: Northern Ontario, Canada
Year: 1990, 1999, 2000
Model: Cherokee
Engine: 4.0
hmm, i have both the chevy 231 and the dodge 231 and a few jeep 231's lying around. i never knew or even thought about the internals.
i might just have to do this.
will this set up still work with a d300 as a doubler?
i might just have to do this.
will this set up still work with a d300 as a doubler?