General interest question...

[Scotts' Yard Care]

Just out of curiousity, what makes the moaning sound usually found in hydro units? This seems to be present all the way from the tiny lawn mower units up to field combines and swathers :D

[fixer67]

Just out of curiousity, what makes the moaning sound usually found in hydro units? This seems to be present all the way from the tiny lawn mower units up to field combines and swathers :D

You could be referring to "pump whine". This is caused when the pump is not 100% in neutral. Pump whine is often accompanied by "creep", where the unit will want to go by itself. Now any time you have a fluid following though a hose or pipe you are going to get noise from the hoses and pipes as the fluid goes though them and this is just the normal sounds of a hydraulic system

[Scotts' Yard Care]

I was thinking of the sound the hydros make as you slowly engage the system for forward or reverse motion. One of my hydros had the problem you mentioned until I adjusted the linkage between the stick and valve body lver.

[fixer67]

I was thinking of the sound the hydros make as you slowly engage the system for forward or reverse motion. One of my hydros had the problem you mentioned until I adjusted the linkage between the stick and valve body lver.

Then you had "pump whine". I see this a lot with hydro ZTR machines