Jeep Enthusiast Forums banner

NP231 Inspection Items, what to look for?

5K views 6 replies 4 participants last post by  RT91 
#1 ·
I have my NP231j from my 94 yj, 4.0, manual trans, apart to find the source of a noise that is killing me. There is nothing that is obviously wrong with it to me upon initial inspection. Stress "TO ME" in that statement. I am not a professional driveline mechanic and since the noise is real and I haven't found anything wrong... You get the point. I just posted a different thread about the noise/diagnosis issue and that is NOT the point of this thread. The point of this one is to hopefully help others answer the questions I have been trying to answer for the last week or two. (I really have tried and tried to find the answers before posting a question. To the point of obsession. Ask my wife! lol) Anyway...

Here are a few questions I have not been able to find the answers to:

1., When inspecting Range and Mode fork pads, what should they look like? What do they look like new? How thick are the pads when they are new vs. when they are functionally worn out?

2., Should there be ANY play between either fork and the rod they are on? My range fork is the cast aluminum type with three pad points. Both my forks have a little bit of play between them as if they were bored out a few thousandths too big.(Both mine look fine, but I don't necessarily know WTH I am looking for.)

3., Should there be any "play" in the planetary gear assembly? I am doing this with the case in the jeep so the planetary gear / input shaft is still in the case. If I grab it with my hand, I can wobble it around a little. Rotation feels smooth. Very slight in-out play. Is this normal?

4., With the main shaft/gear hub assembly out, if I rotate it back and forth on it's "x" or horizontal axis (Vertical does the same but I wanted to be clear about what I am describing), like it would rotate in the case, the brass gear rotates freely. The tabs on it that limit it's rotation are about half the width of the gear that it resides in and it gives it enough travel to make a metal on metal "click" sort of noise when rotated. When rotated back and forth rapidly, it makes a very fast click or chatter (Which it just so happens it the noise that is coming from my t-case). Is this normal?

Answers to these questions (and others like them) will make the difference between getting stuck for hours or days on items that are non-issues and finding the real root cause of the issue. They could also help us all save money when we replace ONLY the BAD parts.

Generally speaking, from the types of questions I am asking it is safe to infer that I have decent mechanical ability but lack specific item knowledge. In order to help those like me (or US as it is probably more appropriate), When taking apart a Transfer Case to inspect it for repair, what should one look for in more specific terms? e.g.; My filter is clean, I found no more than a slight sparkle in the bottom of the case and no real metal shavings, my chain isn't "hanging" off (although I am not sure what it should look like), the bearings all seem to rotate smoothly, gear teeth all look(to me) to be perfect, etc... Those general items/issues have been covered a billion times in as many places but what hasn't are specifics like I asked in my previous questions.

I and hopefully others will probably have more questions as well.

I know there are lots of pictures of build-ups and tear downs all over the place but try to find a really good picture of both range and mode fork pads, installed on the fork, NEW, to see how much "meat" they should have to them. Now take the few pics that you do find and try to verify that they are what your specific model should look like and you may see that your confidence begins to wane. PICS of parts, wear points to look for, common wear items and how to tell when wear has become and issue, etc... will be very helpful. A broken clip is pretty obvious. A bearing that is out of spec may not be. You get the point.

I would like to see this thread become a very useful tool for all us YJ'ers (and TJ'ers. Anyone with a 231). That being said, this thread and all others are only as valuable as their content. Speculation will not be very helpful here for this purpose. PLEASE, ONLY COMMENT ON QUESTIONS IF YOU REALLY KNOW THE ANSWER. I really hope you understand where I am coming from here. In no way do I mean to be rude. There are already a ton of threads out there about transfer cases with lots of speculation and "Maybe/Might be games". The lack of certainty in those threads is also the reason there ARE so many threads. We can really make this a great resource if we stick to the facts. We'll all benefit.

OK, Hopefully this gets a few replies! I know there are plenty of you on this site that really know your stuff!

Thanks in advance.

Eric
 
See less See more
#4 ·
I have never seen a brand new 231 open but I know mine works just fine and there is a teeny amount of play in the forks and a little in the shaft but not really enough to see it move but you can feel it. The pads were maybe 1/8 thick.

I think you are not getting response because there is too much text. I know you want to give details but eyes glaze after a paragraph.

What is the noise you are hearing? Have you narrowed it down to the x-fer case?

Could you take a video with sound and post it on youtube?


Do you have pix of your internals?
 
#5 ·
I have never seen a brand new 231 open but I know mine works just fine and there is a teeny amount of play in the forks and a little in the shaft but not really enough to see it move but you can feel it. The pads were maybe 1/8 thick.

I think you are not getting response because there is too much text. I know you want to give details but eyes glaze after a paragraph.

What is the noise you are hearing? Have you narrowed it down to the x-fer case?

Could you take a video with sound and post it on youtube?

Do you have pix of your internals?
I agree and I had a feeling that would be the case.

Quick run down, I have a clicking noise that I can only hear upon deceleration whether in gear or neutral, clutch in or out, makes no difference. I put the t case in Neutral and put the trans in gear and let out the clutch with the engine running. Then I crawled under it with my stethoscope. I listened to both the trans and t case, everywhere. The noise is DEFINITELY coming from the tcase, next to the detent plug bolt, a couple inches toward center. It's not perfectly rhythmic so it could be called a rattle or a click. More of a clicking IMO. I don't have pics but this morning I took all the internals, minus the planetary assembly (I did it in the jeep and didn't unbolt it from the trans) to a local jeep junkyard and they said that everything looked amazing. The PO must have replaced the chain and everything else looked exceptional. I am thinking it's either the one thing I didn't take out or it's F'ing magic. It's driving me nuts though. I could wiggle the planetary assembly a little though. Is that normal?
 
#6 · (Edited)
Eric-your post is well written, and you describe everything very well. For those on the forum who have T-case experience, all your descriptions sound appropriate. I don't mind reading at all, and my eyes glaze only when people can't punctuate or spell. And yes, I don't mind typing a lot either. I do hope that I am able to help you, but my FSM is in HI, and I am in the desert. If you look at my SYE install thread from the FAQ which I will edit in later, you can see my shift pads, they are only about 6 months old from my prior rebuild so consider them new. Edit--http://www.jeepforum.com/forum/f12/sye-install-np231-still-695330/
Being an infinite skeptic, but not an infinite critic, I have a few questions. I know you feel certain the noise originates from your T case, and I can only assume you have ruled out your U joints which are a common cause for odd noises. Likely you took off both drive shafts one at a time, and tried to duplicate the noise and have ruled these out. Working thru this process will be more of a ruling things OUT operation rather than ruling things in. The brass gear you described, this would be a synchronizer ring. In operation, it does not oscillate back and forth, but turns at the same time as the whole rotating assembly. It is able to move rotationally back and forth within the limits of the synchro tabs but only under load per se when the shift hub is slid over the top of it. I am not certain of the specs which describe how much your shift forks should move/wobble on the shaft, but there is a certain degree of motion and they are not rigidly joined to the shaft. Just make sure they are securely fixed to the shaft, and the connectors aren't loose, damaged or broken.
While you have your case apart, go ahead and pull the rest of the transfer case off of the back of the transmission. It doesn't add too much to the work you've already done. Start up Jeep and let it idle, run thru tranny gears and see if your noise persists--this is the painful part of ruling things out, and this may help rule out a further drive train source even though you are certain it's the T case.
The motion you describe in the planetary doesn't sound abnormal for the partially disassembled condition. It doesn't have much if any support at the back end when the rest of the guts are out of the case.
If you're suspicious of the synchro assembly, then replace that on your reassembly, see if it still makes the noise, etc. This isn't likely going to be easy to find the clicking noise source but I believe you have the proper analytical approach.

You have a PM
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top