Converted NP203 grinding sound in 2WD

coolpup32

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I'm thinking, while you're working at the rear diff, i'll work the rear-output on the tcase. we'll split the work and one of us will find a solution.

If weather permits, i'll pull mine tomorrow :headbang:
 

FitzK25

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Sweet well, I’ll definitely get back to it this week and I’ll let you know what I find. Looking forward to your discoveries haha
 

AuroraGirl

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IT HAS GEAR OIL IN IT?


I found this on a google search since its from someone with more experience than myself, but here you go

2 reasons.
1. The chain requires a thiner oil to lube especialy in cold climates
2. There is a pump in the tail shaft that feeds oil to the rear bearing for both lubrication and cooling. It's basicly a plastic spiral gear like a speedo drive. Gear oil when cold tends to bust that pump and the end result is the rear bearing runs dry and over heats and burns up.


There is a lip in the tail housing that catches oil slung of the chain. The diferential in the tail runs in it and the pump for the tail shaft gets it's oil supply from it. When you convert to part time you MUST put the case in LOC 10 miles every 200 miles to get the chain turning so as to refill this resivior or you will again trash the rear bearing.
Motor oil in the 203. Same flavor you run in your engine is fine weather it be a 10w 30 or a 20w 50. The multigrades will not hurt the case infact they may be better for the same reason as they are in an engine. Multi grades were not common in the 70's when the 203 was produced is why the manuals state 30 weight. Yes in cold climates ATF would be something you could use since it is less effected by low temps but a 5w 30 might be a better choice.



some thoughts: ATF would be whipping up a storm in a system where its not submerged like an transmission usually has its chain(s) in submerged or separately pressure lubed parts.

ATF whipping up air is NOT good for heat and lubricating and your seals would probably not like ATF after so many years, however, this is my theory here. i only mention it because the thing I posted above did and The NP203

I typed most of this then left to do stuff and forgot, so it may seem abrupt but put the right fluid in. if someoen has not said that now
 

coolpup32

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Thanks Aurora, I'll pay close attention to the pump, it being broke sounds plausible
 

coolpup32

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I'm going to embed all the images i took today, but look closely at the needle bearings (Pics 5&6) and the thrust washer? (pics 8,9 & 11). The teeth are chewed on pics 2-4 but i dont believe thats the source of the sounds i'm hearing.

with the tail housing out i spun the output and it bound up a few times, only spinning easily in one direction. I beat on it and piece of a washer dropped out (pics 5-6), it spun freely a few times and seized again, beat it again and another of the tiny bearings dropped.

I cant get the nut off the yoke, my largest 1/2 in socket (1 1/8) is too small
edit: did some research, looks like this nut is 1-5/16. O’Reilly has one for $10. i'll pick it up tomorrow

i'm pretty sure the large needle bearings dropped when i separated the tcase, understandably. but where do those tiny bearings go? its not many, so i guess the rest are in the bottom of the case or my catch pan

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RaisedK5

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Those little bearings are part of the trashed thorington bearing dangling from the shaft. Probably a good idea to take the rest of the tail housing apart. Probably sent a couple thru the rear bearings. Looks like an old superwinch part time kit. That's what I had in mine untill I went doubler. Hope you can find a new bearing.
 

coolpup32

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Looks like an old superwinch part time kit. ... Hope you can find a new bearing.
Mine is a rancho suspension kit, i still have the box. i have no clue what a thorington bearing is, googling now. oh goodness, are these hard to find? I was only under the assumption the chain was hard to get!?!?!?
 

RaisedK5

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That's the one. Shouldn't be impossible. They probably used a common bearing, just have to figure out the number for that one.
 

FitzK25

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Ahhh, well that looks like a pretty likely culprit. I believe that torrington bearing is what comes with the MM 501 kit, if you look at the spacer on this page: Should be able to get one that way if you have to. When I get into mine I'll let you know if it's the same problem - I bet it is. With that spacer destroyed, I imagine the 4wd selector ring and the differential drive gear can drift into the differential assembly and make that racket, amongst other things. https://milemarker.com/product/501/#prettyPhoto
 

coolpup32

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... With that spacer destroyed, I imagine the 4wd selector ring and the differential drive gear can drift into the differential assembly and make that racket, amongst other things. https://milemarker.com/product/501/#prettyPhoto

Oh yes, that makes perfect sense and explains why the teeth are chewed up also, and why the previous owner said it didn't make sounds in 4hi
 
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coolpup32

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Just a couple of updates on my end...

- The 1-5/16 socket i ordered from oreilly auto worked perfectly
- I ordered the 501 kit from MM. I think i have the original internals of the np203 so I plan to convert from rancho to milemarker.

I was concerned about the 2 bearings in the tail housing. i cleaned them up and cannot see any scratching / pitting etc. So i'm going to leave them in place. I dont have a press, so this works out for me.

My parts washer pump has failed, so i'll spend the next couple of days with degreaser and wire wheel cleaning up the casing while i wait on the milemarker parts.

I feel lucky, it not being the chain or something expensive, i hope you have luck as well @FitzK25
 

coolpup32

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I'm having trouble cross-referencing this bearing. Can anyone help? Its the rear output bearing, closest to the rear driveshaft. after more cleaning, it feels a bit crunchy

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RaisedK5

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