Kubota ZD21 rear axle fluid level issue

[Jbush]

I purchased a ZD21 zero turn second hand last year, machine currently has 790hrs. Mower is in very good shape and appears to have been well maintained. I’ve had no issues so far but yesterday noticed a small wet spot under the mower. It appears as though it’s leaking from the back right axle fill plug. When I removed the fill plug an ounce or so of hydraulic fluid came out. Level was slightly above the fill plug. The left side is right at the full mark and the trans check under the seat is just above the full mark. Fluid appears to be clear and in good shape. The mower has been sitting for 5 days since last use and it didn’t give me any indications of a problem then. I ran the mower for about 5min checking all functions and then re checked levels and again the back right axle level was above the fill plug. I was under the impression it was all the same fluid and can’t make sense of why it’s higher in that axle than the other. Will operating the mower with level that high hurt anything? What could be causing it? Any insights would be greatly appreciated.

 

[Workerbee]

Each final drive is a seperate reservoir. They all use udt but you could put 80w90 in the final drives if you wanted. Not in the transmission though. Only udt or sudt2 in that one.

 

[Jbush]

Thanks for the clarification. Any idea why level would be going up in one of the final drives?

 

[Russell King]

Try to measure the level when it is cold. Then use it and see where it is when hot. Leave the cap off for a little while and then see where the level ends up at.

There may be a plugged up vent that is not allowing the level to settle back down or pressure to build up and force the fluid up into the tube where you check the level.

That is all I can think of about the problem