NP231

So I'm looking for a new tcase as mine blew up last weekend. I was wondering if the NP231 ever came with a different spline count, or gearing, or model. My tag on the side of my tcase reads NP231J. What does the J stand for?

Yes different auto or manual. Manual input is 21 spline and auto is 23.

killer98xjsport said:

Yes different auto or manual. Manual input is 21 spline and auto is 23.

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you sir are wrong, it is a date split. I used a amc 231 instead of a 231j. The tera 2 lo for the 231j fit and works so the guts are the same. someone will chime in on the date split for the spline count

Well I'm looking for a new case with good guts inside of it. I have an automatic that uses the 23 spline NP231 J. I have an SYE kit that is going to be installed into the new case. Therefore, even if I pick up a 21 spline case, wouldn't it still work as I'm replacing the main shaft with the SYE case?

J is for Jeep.

Different version of the 231 were used in Chevy and Dodges. A Heavy Duty version was used in the military HUMMV, with a six pinion planetary set and a wider chain. Any HD SYE upgrades the output shaft. Jeep Cherokee 231 are all geared the same. The were internal changes and input spline count changes so you have to be careful buying a used one. In most cases you can mix and match internals to get what you need.


A quick search on Google.com finds plenty of info -

http://www.4wheeloffroad.com/techar..._jeep_np_231_transfer_case_rebuild/index.html

http://www.madxj.com/MADXJ/technical/technicalfiles/JAtCaseUpgrade/tCaseUpgrade.htm