Oddmodman Posted October 20, 2012 Share Posted October 20, 2012 Hi guys, so here's the deal. I have a 1990 AX15 with a bad NP231 (chain broke, cracked the case, etc). I also have a 1987 BA10 with a good NP231, but the tranny itself is bad. So, what does it take to put the good NP231 from the French POS onto the good AX15? Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 20, 2012 Share Posted October 20, 2012 A 15mm wrench....and there is one 11/16" nut too. The spline count should be the same. It should just bolt on. After you remove the drive shafts you should just be able to remove the old, and slide on the new. Before you do make sure you've done everything to the "new" T-case tha you want to do, like replacing the vent hose, any seals you want to replace. Getting to those things once the t-case is installed is a PITA. Link to comment Share on other sites More sharing options...
apexjeepinjoe Posted October 20, 2012 Share Posted October 20, 2012 Spline count is different. You need to change the shafts. Link to comment Share on other sites More sharing options...
Oddmodman Posted October 21, 2012 Author Share Posted October 21, 2012 The input shaft is the connecting shaft between the transmission and t-case? Link to comment Share on other sites More sharing options...
johnny quest Posted October 21, 2012 Share Posted October 21, 2012 yup. some are 21 spline, some are 23 spline. Link to comment Share on other sites More sharing options...
alleydog Posted October 26, 2012 Share Posted October 26, 2012 Actually you change the input on the 231. The newer case will have 23 splines and the older case will be 21 splines. Link to comment Share on other sites More sharing options...
NotMatt Posted October 26, 2012 Share Posted October 26, 2012 Yes, the older case on the BA10/5 has a 21 spline input planetary bearing, and the case that's behind the AX-15 has a 23 spline input planetary bearing. You'll need to take both t-cases apart and swap the planetary bearing (assuming it is good) out of the junk t-case into the good one. If you're not comfortable tearing down the t-case to do the bearing swap, then it's probably going to be easier to find a used 23 spline unit rather than doing the swap. You'll need some good snap ring pliers, and a good clean bench to work on if you do decide to dig into it. Link to comment Share on other sites More sharing options...
Oddmodman Posted October 26, 2012 Author Share Posted October 26, 2012 I'm going to go for it. Nothing to lose really at this point. Besides, my dad, the real mechanic, will be helping me. Thx all. Wish me luck! Link to comment Share on other sites More sharing options...
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