HOW TO: Replace a NP231 Chain

so for those of you who offroad your jeep, and even those who dont...the time will come when your transfer case chain will stretch to the point of needing to be replaced. or else you may end up skipping teeth while in 4wd and damaging gears, or have the chain slapping around and damaging the case. this write up is for an early NP231 case, but the same basics steps apply to almost all chain driven cases.


so here's the how to.

drain and remove the tcase from the jeep and set it on a workbench (or ground if needed). you can do the whole job with the tcase still in the jeep if you want. but its more comfortable and easier to work on out of the jeep....and besides, its only 6 more nuts to remove the case.

step one: remove the front output shaft yoke.


then turn the case over and remove the 3 15mm bolts to remove the rear output shaft housing. ( later model NP231's will not have this housing, so skip this step.)


Next, remove the speedometer gear. 13mm bolt. remember which way it is clocked when you remove it, as you will need to put it back in the same way.



now, remove the c-clip from the mainshaft. (later model NP231s will need to remove the output shaft seal to get to the clip)




then, unbolt the 5 15mm bolts that hold the housing on, the housing may require a little prying and some light tapping with a hammer. but dont get to rough, it is only aluminum


remove housing and you will see the oil pump.



remove the oil pump



now, remove all of the bolts that connect the 2 halves, one of them is a 12point 10mm socket, you can use a wrench...but i suggest getting the socket.


there are 2 pry points for the case halves that you can put screw drivers into. pry the case apart.


now you will see the chain and gears, and if you're like this one the chain will have a TON of slack


lift up on the front output shaft and the mainshaft until you can get the front shaft to come out so you can remove the chain.



and because of the severity of how badly this chain was worn it ate into the case and tore up pickup filter. will need to be replaced



this one also had worn out fork sleeves which will also need to be replaced


this is also a good time to check over everything else in the case for damage or excessive wear. and also to give everything a good cleaning.


heres the case parts all cleaned up.


and heres all the new parts going in


new sleeves installed


and now to start putting everything back in, remember to put the spring back on the end of the selector fork!





and also make sure the magnet goes back in its place


now put the chain on the front output shaft


and lift up on the mainshaft like you did to remove the chain, and install.


and make sure eveything is seated in place


i installed the new pump filter onto the old tube, and set it into place on the back case half



apply RTV around the edge of the case half



let the RTV sit for a minute or two, then put the other half onto the case, now bolt it back on.


install the oil pump, and use a screwdriver or a pick to insert the pickup tube into the pump




apply RTV to the speedo housing.


install and bolt on



now install that c-clip



apply RTV to the housing and install and bolt on the tail cone housing




install the front yolk



install speedo gear in original position



now you should move the shift lever by hand to make sure everything moves and engages the right gear selections.


now would also be a good time to replace the tcase input seal if needed



now your tcase is done, and you're ready to reinstall back into the jeep.

Thanks for posting. I love how to's

was that troys

No looked like stock chain.

I did notice u didn't put rtv around bolt holes on transfer case half. In my experience that will cause a leak eventually. U did do it on the speedo housing though.

eh, in my experience the 1/2" width of RTV around the case half is plenty, and the fact that i let it cure for a while before pressing the two halves together makes a really nice seal. which makes RTV'ing around the bolt holes unneeded.


also, the amount of prep work i do between the sealing surfaces to make sure they are 100% clean, scuffed, and free of ANY oils makes sure my work stays dry.


speedo housing is a different story though, because it doesnt give you the same space for sealing. so going around the bolt holes becomes needed there.

MudRaider wrote:

DIRTY wrote:was that troys

Nah, Nick posted this back in December. BTW, is that the "bigger" chain you guys all tlk about Troy needing to put in?

this was just a standard OE rebuild.

Awesome job. You make it look easy...LOL

I have done this a few times. This is a great step by step.

Great pics!

Thanks Nick. I have to do a SYE on mine and this gives me an idea.

Pitbullguiller wrote:Great pics!

Thanks Nick. I have to do a SYE on mine and this gives me an idea.

im pretty sure i have a writeup out there somewhere of how to do a full SYE, if you want it i can try to track it down

Full SYE write up....want it or not....hmmmmmmm




Of course we want it. Is it done yet? Is it done yet?

Nick@HappyTrails4x4 wrote:

Pitbullguiller wrote:Great pics!

Thanks Nick. I have to do a SYE on mine and this gives me an idea.

im pretty sure i have a writeup out there somewhere of how to do a full SYE, if you want it i can try to track it down

That would be great!

I dont have to remove t-case to do it right?

I have heard you can do it without removing but I bet its easier to work on a bench rather than off ur back. I will be removing mine for my SYE.

very nice...making it a sticky.