I drained the oil, and removed the oil filter and air filter. The oil filter is like nothing I've seen before. It has inner and outer screens in the bottom portions. There is a little dirt on them. What's the best way to clean them? and then what about the upper portion? is there more to be dismantled and cleaned? How is this filter work? The upper part is heavy, and one small line entering the top, the lower base has 2 large lines running to it. I'm wondering if I there is another drain besides the drain on the pan. I have a lot of dirt to remove.
The oil bath air cleaner had non-detergent oil in it. The dirt (a lot in there) settled out in the bottom. Is non-detergent oil the preferred oil in a oil bath cleaner? Detergent oil would have held the dirt more in suspension where only the heaviest crud would have been on the bottom. Which is preferred?
Thanks

I am not sure what you have for a filter. It could be a after market filter. But putting it up top again maybe someone will have more knowledge will respond. I have been around RD Cats that still had screens rather than a filter for the diesel fuel. But never just the screen for the engine oil.

I have never had anyone tell me one oil was better than the other Iin the air cleaner. I have used what ever I would put in the engine. I have used all the part full quarts and gal jugs that seem to accumulate with just a bit that did not fit in things as added oil. Back in the 70's maybe 80's super filtration units where advertised, as to cleaning and reusing your engine oil. Which I never heard anything good about. But it was kicked around it could be good for air cleaners. But I don't know of anyone doing it all the used regular machines had dry air cleaner elements by then.

I looked thru my pictures I have stored for the dozer, and I don't have any showing the filter on the machine. I brought the filter home to clean, and will post some here. I did a search looking for anything about this filter and did see a picture, and others talking about bypassing the lines entering the base the filter is a part of. So I think the filter is factory, at least that is my guess. If it is an add-on it looks to me to be from an early filter design, but the way it's mounted the base is a part of the engine. I'm going from memory on this as the dozer is about 1.5 hours away.
The reason I asked about air bath oil in a air cleaner is the filter coils  where the oil is drawn up into was really clean as was the non detergent oil in the pan. That oil smelled very old and was a gray blue/green color but didn't look dirty, but the cup was full of insects under the oil and the almost half inch of dirt on the bottom was solid. I thought that since the oil was able to stay clean because the dirt settled out maybe non-detergent was possibly better. I have always used leftover new oil in my jeep oil bath like you described.  

I'm not sure why double pictures got in there.
I put the spark plug box in there just to give some reference.
The top portion of the canister shown is surprisingly heavy, and wondered if it's supposed to be removed for cleaning

That filter unit has the optional secondary filter used with the original bypass filter.
 
 

Thanks for the diagram. It looks like that element should be cleaned in there. By the looks of my filter, I don't think it has been separated in a very long time. By removing the bolt on top will it separate? I'm concerned if I do get it apart that I might not be able to keep it from leaking, especially if finding a new gasket is a problem. Thanks

I realise you are working on a RD4 and this video is for a D2, but it will give you a general understanding of the disassembly/assembly of the component.

Mine looks just like the one in the video except the base is still on the tractor. That long tube he used the made socket on stayed on the base on mine. It looks like mine should just unscrew, but it won't come by hand like his did.

The 5B8934 element is the disposable type and should be changed with each oil change. The element is still available along with alternative manufacturers.
What is the s/n of your tractor?

I posted pictures of it earlier this year. I remember the 1919W. I've had so many other things to do, I haven't been able to get on it like I would like to.