:dance1:Over the years Yanmar has wavered on what they recommend for the front diff. Looking through their literature from then, Yanmar has recommendations for the FRONT DIFF oil ranging from 90wt gear oil to 30 wt motor oil.
I waver too....and in our machines I tend to go back and forth between 20w50 motor oil and 80w90 gear oil in the 4wd front axle - always at least making sure that the gear oil is GL-4 or GL-5 type. Oddly enough, both the multiweight motor oil and multiweight gear oil are pretty close to the same viscosity at the same temperature.
Even though Yanmar invented and patented that tricky bevel gear driven front axle that most all 4wd tractors use today, I sometimes wonder about their choice of front end oil. I'm not sure that that Yanmar put enough thought into folks using their tractors as 4wd snowplows in cold climates. Although for Ag use and ag climates, I'd agree with Yanmar that it the front axle oil could be either type. What I'd really like for cold weather/high stress on the front axle bevel gears would be a 50W90 GL-5 Gear Oil with an anti-foaming additive. But that's being picky. Truth is, I've not heard of any front axle problems happening when there was any kind of oil in the front axle. The problems come from water in the axle and especially from not getting the water drained out well because it sits down under the oil.
The standard shift tranny, rear end, and hydraulics are a different story. They all share a common sump and oil supply and the kind of oil is important to them....which is kinda crazy since the requirements for the type of oil that each one uses are way different. For the transmission and rear end we want high shear strength at all temperatures where for the hydraulics we don't care so much about shear strength as we do about flow characteristics.
Luckily, a whole lot of today's tractor and heavy equipment industry use that nutty shared sump setup & as a result there have been some really good combo Trans/hydraulic oils developed. On the downside, the good ones sure are expensive oils to buy and that has led to a lot of copycats. There are standards, but no enforcement.
JD 303 used to be the oil everyone pointed to as a standard combo trans/hydraulic oil, but not anymore since it was an archaic mix made from materials no longer available. Today, it is mostly the economy oils that reference JD303 and that might be simply because there is no longer a valid JD303 standard.
So what I use in my own tractors is a trans/hydraulic oil that is sold by a company who manufactures their own combo transmissions & hydraulic systems. That's things like JD HyGard, Allis-Chalmers , Kubota, International Harvester, etc. Right now I'm using JD HyGard in some and New Holland Multi-G 134 in others. All today's combo trans/hydraulic systems are pretty similar mechanically & I figure any company that makes their own trans/hydraulic systems probably has a vested interest in specing an oil that works well in them.
Personally I wouldn't use generic non-name-brand trans/hydraulic fluid from the local cut-rate tractor supply store in my own machines.... but I gotta also say that I know plenty who do and don't know of any problem they've had from doing so.
rScotty
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