NP231C and NP231J Transfer Case Differences

This video is about some of the differences between my NP231J transfer case and the Np231C transfer case. Now If i had a NP231c Hd then it would have had a six gear planetary along with the 1.25 Transfer case chain. But that is nothing to worry about as i'll make a 6 gear planetary

[shanemancuso]

Nice info. I did pretty much the same build except I used a 231c out of a (82-94) s10 blazer which already had a fixed yoke front output with a 1310 u-joint. It had the 1.25 inch chain too (I dont know if all of them do or not). The early 231c's also have an adapter to go to an early 4l60e/700r4 4 bolt flange, which also incorporates a trans mount location. I was mating it to a later style 4x4 4l60e (LS style) so I bought an adapter from Advance Adapters (50-0405E is the part number) to convert the later 4l60e (LS style) to the early style 4 bolt flange, it also comes with a tone ring that mounts on the output shaft of the 4l60e for a gm style vss and they threw in a napa vss. So that would give you your correct gm vss signal. You would have to run some sort of low range input to the computer so it knew when it was in low range, or just live with your speedo being off in low range. I Retained my factory Cherokee gauges, so i didn't use the vss in the adapter. I used the back half of the 231j along with the Advance Adapters sye. The spline engagement from the trans to the t-case wound up perfect too, so it all worked out pretty nice. Good luck with the project!

[njhockey]

Great video. Question, I have a 2002 Wrangler with the 4.0 and a NP231J TC. The TC cracked over the winter and I bought another TC from a salvage yard that was also on a 2002 Wrangler 4.0. That Jeep only had 70K miles on it. I bought that TC. That TC is also a NP231J but it only has 4 lugs to mount to trans. Is it ok for me to just utilize the 4 lugs or do I need to figure something else out. Thank you for your time and keep up the great videos.

[hlubojg]

Is the front output spline count the same j case to c case my 231c has a fixed yoke can I just put a jeep yoke on it to use the front jeep driveshaft?

[darrentylor]

You should use the jeep selector(left one)... It offers true neutral... Otherwise you should not tow it unless you take out the driveshafts... Jeep ppl with older 231 only had the non notched option but they are interchangeable and offer you a safer towing option

[christianp]

Did you end up using the Jeep or the Chevy shift fork?

[mikepednault]

Will it matter if the NP231C is electronic shift vs floor shift if mating with an NP231J?

[RussellBooth]

The Delphi ECU can be reprogrammed by GMs Tech 2 unit to put out an accurate speedometer reading whenever the diff ratio, etc is changed.

Mine was changed back when it was brand new in 2003 when the first owner got a set of 3.91:1 diff gears fitted to replace the factory 3.46:1 diff gears in my Commodore.

My speedometer is electronic & its signal comes from the ECU, not directly from the speed sensor.

The ECU was recalibrated on an on car Dyno after they also fitted a set of custom headers & twin 2.25 inch cat back mandrel bent exhaust system.

It has an off the shelf twin 2.5 inch cat back exhaust system fitted now that needs replacing again, I want to get a set of brand new 1 5/8 inch Genie headers, 200 cell cats & twin 2.5 inch straight through exhaust system.

At 16 1/2 years of age I think it needs all redoing as the last muffler guy just grafted the last exhaust system into the old one by cutting the flanges off & straight welding it onto a set of cat pipes which he made up.

There's a restriction I want to remove before the cat converters so the cheapest & best way to fix that is to replace the whole exhaust system.

The headers have been patched up & are a bit Rusty as well !

[txsviking]

Overall there are quite a few differences.