I had originally made a post with questions concerning the NP233-NP231 TC swap, but have since decided to instead to just use a jeep TC shifter assembly to shift my 233. This comes with a new question.
If I do this, will my front axle still engage or do I need to build a cable to replace the vacuum actuated system? Some places people mention this but on the thread where that guy attached a wrench to the transfer case he doesn't say anything about engaging the front axle. Other than this and the wiring for the 4Lo, is there anything else I need to be worried about?

 

This is awesome to see as I've had the same thoughts. From what I see of working on these vehicles the front vacuum actuator that's underneath the battery is activated by a switch on the tcase itself when the internals of the tcase shift. So as long as your vacuum lines going to tcase from engine, and from tcase to vacuum actuator are in good shape. If the transfer case shifts so does the front axle. (Note) Pull top plug on tcase to check front tcase front seal. If fluid comes gushing out front tcase seal has failed 100 percent and front axle will most likely not function as vaccume lines fill with trans fluid. Your Trans will get destroyed as well. I'd recommend replacing it as prevantative maintenance. Its not terribly hard and ive now come acrosss 2 with total failure at 180k. Just replaced one on my Dads new zR2 and the rubber was as hard as concrete. The electric plug on front axle should be the 4x4 light on guage cluster if equipped only.

 

Dude you rock! that's exactly what I was looking for. I'll for sure check the T case seal. Thanks!

 

I just pulled the fill plug on the transfer case and about 3.5 quarts of ATF came pouring out. I've also been having issues with the HVAC system so that explains it. Crap. Thanks for the tip, you probably saved my transmission 🤣

 

Hmm.... guess it could if you pulled Trans fluid up thru the front diff actuator on the tcase all the way into hvac lines. My guess is you have bad vaccum lines by brake booster. There's also a small vacuum box inside drivers fender by booster. It's connector is very short and easy to unplug.

The actuator on tcase fills with Trans fluid when front seal fails. Just remove and clean with brake fluid. It's a 3port thread in plug. Vacuum line is directionally installed with a small male pin that lines up with on the vacuum hose assembly for correct assembly, but can be installed in any position. It's a pita but I believe these vacuum lines are the reason everyone is always chasing the vacuum actuator for front diff. I'm on my 6th S series last generation and have yet to see a bad vacuum actuator. I've seen dirty corroded tcase Control module in the passenger kick panel on every one.and bad vacuum lines on 5 out of 6. I've seen bad front differential activation gears on 3.