What is the purpose of having a Hydraulic Oil Filter and a Transmission Oil Filter?

[josiahgarber]

I was looking at my scheduled maintenance for my Kubota L4701 and noticed there is a Hydraulic Oil Filter to be changed at 400 hours and a transmission oil filter to be changed at 50 and 200 hours.

Why are there two filters for the same type of fluid? Are those fluids isolated from each other?

Probably a very simple question, but I appreciate your help.

 

[RjCorazza]

My guess is that the transmission filter (suction) is a coarser filter, and the hydraulic filter is much finer. It is one common sump.

 

[Rockbadchild]

one is a suction filters the other is a strainers

Filters are used to remove contaminants that are smaller than 50 microns, while strainers are used to remove contaminants that are 50 microns or greater.

 

[Roadworthy]

My guess is that the hydraulic filter is there to keep your hydraulic system free of debris. The transmission filter is for your HST to make sure no really fine particles damage the fine tolerances inside. It is all from the same fluid reservoir just an added precaution for your HST.

 

[MAX-24-Dean]

one is a suction filters the other is a strainers

Filters are used to remove contaminants that are smaller than 50 microns, while strainers are used to remove contaminants that are 50 microns or greater.

Good post! The naked eye can see particulate size in the range of 40 microns and larger. So you should be able to see contaminants on a strainer.

 

[SDT]

I was looking at my scheduled maintenance for my Kubota L4701 and noticed there is a Hydraulic Oil Filter to be changed at 400 hours and a transmission oil filter to be changed at 50 and 200 hours.

Why are there two filters for the same type of fluid? Are those fluids isolated from each other?

Probably a very simple question, but I appreciate your help.

No. Single sump.

Seperate pumps.

Different tolerances.

 

[crashz]

Both are low pressure filters on the suction side of each pump (hydraulic for implements and steering, charge pump for trans). As SDT said, the systems have different tolerances, so a relatively crude filter is on the hydraulic side and fine filter on the trans side. Once the fluid is picked up at the suction, it's in a separate system until it returns back to the sump.

 

[LouNY]

Your transmission filter is likely to be larger then the hydraulic filter. Lot more flow in your hydrostatic transmission then your auxiliary circuits.

 

[MHarryE]

Hydraulic filter is a suction filter protecting basic hydraulic system and general transmission. Hydro filter is a pressure filter, able to filter out much finer particles that can damage the precision high pressure piston pump and motor of the hydro. Two completely different cleanliness levels required by the gear pumps and gerotor of the hydro charge, versus pristine cleanliness of high pressure piston pump and motor. Notice how much heavier built and tighter torque for the pressure filter of the hydro vs suction filter of the hydraulic system.

 

[mikester]

It's a conspiracy by OEM's to make you buy expensive throw aways at regular intervals. Real men don't waste money changing oil and filters on their tractors.