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Discussion Starter · #1 ·
I just finished my sbc swap and my transfer case is making a god awful sound.. I done the np231c/j hybrid. My question is can I just get a rebuilt np231c and put a np231j mega short sye kit on it to retain the stock speedo? I I have the Jeep output shaft with a stock shortened driveshaft now..
 

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I done the np231c/j hybrid.
what does that consist of? Wide chain?
 

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I'm not 100% familiar with the "231c/j hybrid". I'm assuming you swapped input shafts somewhere along the line. I know NP changed the gear "cut" around the 1993-1994 time frame for Jeep and slightly later for C/D's. If you didn't have the noise before the conversion, I would look at shaft incompatibility.

231planetary-oldontop-post94onbottom.jpg

The teeth on the planetary pinions are more triangular on the later model pinions and are not compatible with earlier cases.

Also, going by your screen name, if you are running an 88 YJ, you'll need to convert to digital speedo as all the Mega/Super-Duper short SYE's use a hall-effect sensor.
 

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Discussion Starter · #4 ·
On the np231 hybrid I just took the back half of the case off the np231c put in the Jeep output shaft and the Chevy chain and the gears on the chain the planetaries wasn't messed with in the Chevy case I did notice a plastic piece was missing on the range fork but I doubt that's causing this sound.. my Jeep is a 95 with electronic speedo. Thanks guys
 

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I also have the Hybrid setup. I used an S10 transfer case. Zero problems. Whatever Chevy parts would transfer into the Jeep I used. It's been some time since I did this. I thought I used all Jeep on the outside. Mostly Chevy S10 on the inside. I used the wider Chevy gears and chain. I also used the Chevy Planetary. Mated to a Super Short SYE.

At the time, my original TC with Currie SYE blew up. I used a second Jeep TC and Chevy S10 TC. Took all three apart. Then reassembled to form one good unit. The Chevy S10 TC was sitting in the junkyard not connected to anything. Unknown which year. The S10 appears to have never been in 4wd. All the internals looked brand new.
 

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There are three parts that have to have the same style gears

The ring gear attached to the case, the planets in the cage and the sun that is part of the input of all three are not new style or all three are not old style you will have issues



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I made a hybrid using a early jeep case with an early Chevy 241 6 gear planet and wide chain and sprockets from a durango 231HD

Since the jeep input and ring and the Chevy planets were all early style tooth cut no issues but I did have to remove the roller bearings and bronze syncro to use the wide chain and sprockets


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I'm not selling mine. Very happy with it. Just saying it's possible. I had never taken a 231 apart before. I threw away the Chevy front half. I bought the whole thing for $90. If you are running Chevy drivetrain can't you just use the whole 231C? Use a Super Short SYE? Skip the weaker 231J parts.
 

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If you use a Chevy planetary with new style profile gear teeth with a YJ front case with a ring with old style profile gear teeth it will fit together but it will self destruct


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Discussion Starter · #13 ·
Yeah I want to just get a np231c and put the np231j mega short sye kit on it can I do that? I don't wanna go to far into the new case.
 

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Discussion Starter · #14 ·
Well I called teraflex and they said there kit wouldn't work on the 231c then called jb conversions and they said theirs would so I just ordered the jb kit hopefully it'll all work ok
 
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