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Sundstrand Hydrostatic transmission type U

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I'm trying to service my Simplicity 3410 tractor hydrostatic drive. It's a Sundstrand series 15 type U transmission. I'd like to verify the oil level is correct and eventually change the oil. I can't find a good description of how to do this.

From what I can see, the only real atmosphere access to the entire unit is at the rear of the tractor on the bottom. There is a cap that can be removed on a tube (roughly 3" long) that right angles in to the drive unit.

There are also two hoses that go from the hydrostatic drive to an oil filter (I can see the name "Fram" on the filter.

So here's my questions:

1. If I remove and replace the filter, how do I replenish the fluid?

2. Is the access area at the rear of the tractor where I would fill the unit? If so,

3. how can I tell if it's topped off properly.

You guys are always a lot of help and I look forward to your advice.

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If you have a 3410H it has a Vickers unless someone else changed it to a Sunstrand. It sounds like that was the case.

The Sunstrand holds 3 quarts of oil. The oil goes into the 3" long tube. It is topped off correctly if the fluid is over flowing out the fill tube. If it has the Sunstrand there is a vent above the axle tube on the left side of the tractor. You will want that open when filling the oil reservoir.

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When you remove vent plug, make sure wiggle pin is free to move about. If it is not free, expect the possibility of oil drips on the floor.

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