I have the I&T manual for YM135 through YM330D, and just purchased OEM shop manual (but I haven't seen anything about front end in there). I am not sure which version it is for (and not sure which version is my tractor really, but that is whole another story). I also have OEM parts manual through last version, printed in 1990s. I can post photo of diagrams here if you want to take a look.
I am *really really* hoping not to have to take apart the rest of the front end. Can I get away with that?
Bearings that came out of the assembly look good to me (you can see earlier posts w/ photos), although a bit crunchy now. I was thinking if I can wash that sand out, I can maybe re-use them, but I didn't see shields (maybe because they are not OEM replacements by PO?). Nevertheless, I preemptively ordered all spacers, wear collars, seals, and bearings from Hoye to do this job, so if you recommend replacing, I am ready for that too. I read somewhere else to pull shields out if there is no channel for gear oil to travel through, but haven't seen anything about pulling just one side out. Can you explain why to pull only one side?
Sounds to me like we have the same books - or close enough. If something is different then no doubt we'll figure it out.
If you can convince yourself that nobody has been into the center section of the front axle then I see no reason to take it apart. Take a close look at the center gasket and bolts to see if they've been apart. Then I'd check the backlash out at the axle ends vs the input pinion by twisting them by hand and making an educated guess as to backlash using what we've already said. If that feels OK I'd might try to gently flush it to get any metal bits out via the central drain plug. And would definitely plan to change oil a couple of times soon after it gets going.
ONE-SIDED SEALS:
You've probably noticed that some of the Yanmar front axles are designed to be three separate oil reservoirs - each with it's own fill port and drain. I'm not sure when Yanmar deliberately went to that 3 separate oil reservior idea. They kind of played with the idea for awhile. You can tell the model axles that bought into the the idea because they tend to have drain plugs at the bottom of the outer gear housings next to the front wheels.
most of the red painted YMs had those drain plugs but I'm not sure about the older green machines like the YM240D.
Some cross-over designs didn't have the outer drain plugs but could drain the spindle housing by pulling one of the bottom bolts that mount the bottom plate of the spindle.
So why separate the oils? Well, all this is speculation on my part. It might be true and might just be my own overactive imagination. But I don't think the 3-separate volume axle system is so much to keep the oils from mixing as it is to slow down wear particles from migrating from one area to the other. Whatever, it's just one more reason why that whole front axle design is crazy clever. Think about it.....the single-sided bearing shield allows oil to lube & cool the bearing, while blocking any metal particles, dirt, and debris from making its way between the different areas. That confines any catastrophic failure debris to one area instead of all areas. Not only is it a nifty idea, but they get it for free by actually throwing away a part (one shield). That's cheaper than free!!
Oh....It's easier to pry off one side shield if you use shielded bearings, not sealed bearings. And shielded bearings allow oil to flow though more easily than sealed bearings do. But please don't overthink this. I doubt it is going to change anything if you use completely open bearings - they'll work fine. You just lose out on a clever way to separate dirt & debris transfer if a problem ever does occur. Other than that, I can't see why it would matter. No biggie.
HISTORICAL NOTE
Yanmar invented that front combination steering and driving axle. They patented it, and for years only Yanmar had that axle. Of course now it is the standard axle on every brand of compact tractor. And after all, that is what patents are designed to do. Patents trade a limited period of exclusive use in exchange for publishing a better design.
The result of that is that today even my Kubota (Yanmar's arch rival) uses Yanmar's dual bevel gear front axle design. I'd like to shake the hand of the guy who designed it. You really have to go back to some of the front wheel drive mechanisms that preceeded Yanmar's front axle to fully appreciate it. For comparison, look at the sliding wear and limited turning angles of FWD designs using Reseppa joints and other CV attempts. Trying to figure out how to drive a front wheel while allowing it to rotate about a kingpin led to some real ugly front axle attempts.
NEW BEARINGS?
As for ball bearings... Come on now; use new ones! Bearings are cheap. Radial ball bearings aren't Yanmar parts; they are universal parts. Every manufacturer buys them from a bearing supplier and specifies them by bearing number. Nobody makes their own. I think Yanmar uses a lot of 62xx series ball bearings, which just might be the world's most common bearing spec. The common sizes of bearings cost less than ten bucks each retail - and that's even with paying extra for the dual shielding and about a 50% for a really top quality bearing with brand names you've actually heard of before....names like SKF, FAG, NSK, etc....Or you can buy cheap knockoffs for half the price but why bother? And why not change them? Especially since yours already feel rough. In your heart you know not worth it. Try McMaster.com for competitive bearing prices.
enjoy,
rScotty
