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rotorwrench · 02-08-2023, 07:22 PM

The Hoo-Dies have a reservoir section and a hydraulic fluid transfer wing & stator section. If a shock has been regularly maintained, a person will know what's in it. Most folks use more viscous fluid in the older units now days due to wear between the stator and wing shaft that increases clearance over time.

If the unit still rotates then the fluid likely hasn't started to turn to goo quite yet, A person can remove and flush them with denatured alcohol to get whatever is in there out. Once they come clean they can be refilled with what ever works for hydraulic oil. Glycerin was used due to it's good all weather characteristics. Mineral oil tends to get thicker when it gets cold and thinner in hot weather where glycerin would hold it's viscosity pretty well in all temperatures. Glycerin does go bad after a period of time and starts turning into a dark messy goo substance and this is why a lot of folks use SAE 90 GL-1 gear oil or various hydraulic oils. I would consider using AeroShell 100 straight mineral motor oil since it is very well refined and is the same viscosity as SAE 90 gear oil. A hydraulic oil of similar viscosity could also be used. Viscosity depends on condition of the unit. The Ford Service Bulletins have a lot of info on caring for the rotary fluid dampers.

02-08-2023, 07:22 PM	#13
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,491	Re: putting oil in houdaille shock The Hoo-Dies have a reservoir section and a hydraulic fluid transfer wing & stator section. If a shock has been regularly maintained, a person will know what's in it. Most folks use more viscous fluid in the older units now days due to wear between the stator and wing shaft that increases clearance over time. If the unit still rotates then the fluid likely hasn't started to turn to goo quite yet, A person can remove and flush them with denatured alcohol to get whatever is in there out. Once they come clean they can be refilled with what ever works for hydraulic oil. Glycerin was used due to it's good all weather characteristics. Mineral oil tends to get thicker when it gets cold and thinner in hot weather where glycerin would hold it's viscosity pretty well in all temperatures. Glycerin does go bad after a period of time and starts turning into a dark messy goo substance and this is why a lot of folks use SAE 90 GL-1 gear oil or various hydraulic oils. I would consider using AeroShell 100 straight mineral motor oil since it is very well refined and is the same viscosity as SAE 90 gear oil. A hydraulic oil of similar viscosity could also be used. Viscosity depends on condition of the unit. The Ford Service Bulletins have a lot of info on caring for the rotary fluid dampers.