NP231 Transfercase

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NP231 Transfercase

Post by mrpat » Sat Jul 29, 2017 10:23 am

Originally was going to just simply rebuild the original 231. But upon doing some research, I figured I would beef it up some. I know it will still be a 231, not a 205,300 or Atlas, but it will work for now. I ended up buying a 1996 NP231D out of a Dodge 1500. There was a change in the gears between 1993-1994, so I decided to just use the Dodge 231 as the one to rebuild. The things I changed on the inside are as follows.

1. True neutral gear selector. The older selector, when in neutral, did not separate the front drive from the rear. With a simple change of the selector, that is fixed.

Non true neutral selector.
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True neutral selector.
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2. The Jeep 231 used a 1" wide chain to drive the front. The Dodge case had a 1.25 wide Chain for a claimed 30% increase in strength.

3. The stock Jeep planetary gear set has only 3 gears. On 231HD's they have a 6 gear planetary. I purchased a 6 gear planetary off Ebay.

6 gear planetary
4. With the conversion kit came a 23 spline input compared to the stock Jeep 21 spline.

5. Used a JB Conversions SYE kit with a 1350 output flange. Included with this is a 40 tooth tone ring to drive the engine computer and speedometer.

Stock 1992 Jeep NP231
Jeep NP231 all apart
Stock Dodge next to the Jeep main shafts. Notice the first gear above the splines is much wider than the Jeep one to accommodate the 1.25 chain and just how much beefer it is.
1.25 chain.
Painting the case halves.
JB Conversions new main shaft.
All together. I decided to use the Dodge front output flange instead of the Jeep yoke.

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