rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 8,297
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
It varies with the machine of course, but there are two common ways to filter. For standard transmissions and power shifts the common way is to put a series of filters into the suction line between the sump and the intake to the hydraulic pump. Often there are two filters in series - one for coarse particles and one for finer ones. Sometimes in smaller old gear tractors the first one of these will be a cleanable screen.
In our Kubota Hydrostat Plus tranny, there is a third filter that is just for the hydrostat. The tractor has a separate pump for power steering, and if I remember right a small amount of pressurized flow is separated from that PS flow and sent to that third very fine filter before going to the hydrostat cylinders and wobble plate. The flow diagram is in the shop manual.
On the Kubota, these 3 hydrauic filters are in a cluster under the tractor hanging from the bottom of the sump - which is about the worst place to put filters, but everyone does - why do they do that??
Anyway I've noticed the special hydrostat filter is heavier & more expensive than the other two. My guess is that part of the weight comes from thicker walls since it has to handle some pressure, and hopefully the rest of the weight and expense comes from some special filter inside.
rScotty