00XJMiami

Hey guys this might seem like a dumb question but I have yet to find the breather line on my NP231 TCase under my cherokee. Help please!

Michael952

On top if I'm not mistaken. Been awhile since I've had mine off

salad

bubbarules1958

On my 91 it runs all the way up to the passenger side E12 bell housing bolt.

00XJMiami

I'm still pretty lost :/ drivers? Passenger side?

bubbarules1958

Top of transfer case there is a vent tube similar to the picture Salad posted. From that location a vent hose will follow the transmission all the way up to the engine bay. I know on my 91 the vent tube is located on the passenger side E12 bolt on the bell housing. Your situation may be different because I am not familiar with the year of your Jeep.

salad

Driver's side, it's above the front drive shaft. All NP231J cases are the same

00XJMiami

Thank you so much! What oil do I use for this transfer case?

salad

Any ATF you want. GM Dexron family, Ford Mercon family, Chrysler ATF+, any multivehicle stuff... 5w30 synthetic actually works quite well. If you have an AW4 transmission keep it easy and use D/M, then you only have one fluid to worry about!

00XJMiami

What is D/M? And 5w30 in a transfer case? Really?

XJwonders

DM = dexron mercon III

XJwonders

And the 231 transfer case aren't designed for use with heavy gear oils.

salad

D/M is, officially, a fluid that is compatible with the Dexron III/Mercon specification. GM stopped licensing a years ago to push the new spec, so all the bottles say "D/M" or "Dex/Merc". The ATF itself didn't change, just the right to use the name lol. Same stuff you put in your transmission (if you have an auto).

Yeah Rockland Standard gear found that synthetic 5w30 actually does better in these transfer cases. Under heavy use the ATF gets so hot it vaporizes out the vent tube! I'm not sure what the practical benefit is for the average user but it's certainly a workable oil. The lubrication requirements of the NP231 are not particularly advanced hehe

00XJMiami

I knew it was something like that just wasn't sure. And perfect! Thank you! I have ALLDATA, but I'd prefer to take advice from the real world on some things haha.

salad

That's correct. None of that junk in there.