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Discussion Starter #1 (Edited)
So I just changed the oil in the gearbox for my mowing deck. I unbolted the gearbox and drained the oil that way. It was easier removing the gearbox from the deck than I thought it would be. Anyhow, after seeing all of the shavings from the tractors hydraulics I was curious about the mower gearbox. I drained the oil through a paper towel and didn't find any shavings or foreign matter :good2:. I did notice that the oil was very dark. I've had it for two years and this is the first oil change to the gearbox. I'm wondering if I might have some kind of contamination (water) in my oil, or if this is just the color of oil JD uses?

Also, a question about the valve on top of the gearbox. What are we venting? If the gearbox gets warm/hot is the small amount of air it there going to make a difference? I haven't looked up the thermal expansion of the oil...so yeah what's the deal with that?
Thanks. :cheers:
 

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It is doubtful there was any water in there. Water in oil normally results in a light brown fluid that looks like chocolate milk. If in doubt you can Google "sizzle test" and give that a try.
 
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As the oil gets hot it heats the air inside the box. This causes a build up of pressure. The vent is there to vent any pressure over probably about 2 psi.
By the way, I have heard some say their vent leaks oil when they store their mmm upright. This vent should not leak. It is not an open to atmosphere vent.

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