Shock Fluid Replenishment

[Bob Bidonde]

A while ago I reported the result of combining glycerin and transmission fluid. They are totally not soluble in each other. I am not going to use glycerin in my Houdaille shocks because glycerine and moisture condensate are soluble. So here is my rationale for topping-off the shock fluid with transmission fluid.
As the transmission fluid is totally insoluble in the glycerin that is already in the shocks, and both are incompressible liquids, then it should be practical to top-off the fluid level with transmission fluid. There is a difference in viscosity between the two fluids, and in the my solubility test, the transmission oil stayed atop of the glycerin. So one downside is that shock behavior may become inconsistent, but not enough to deter me from using the transmission fluid.
What are your thoughts in this matter?

[Kurt in NJ]

I have been using ATF mostly because it is what is in the oil gun, and I did some research into motorcycle fork oils, and in testing it performed good for that viscisity, but multi viscosity tractor hydraulic oil looks better and I hound 1/2 a jug in the shop
I don't know about mixing, perhaps attach shock underneath table and work it to purge as much as possible, mount it normal and work new oil in ---this also has the advantage of being able to adjust the resistance to match the service bulleten standards
The only experience of mixing different types of oil is in ac conversions to 134, there the mixing has been good, have less hose leakage problems and moisture corrosion

[rotorwrench]

Hydraulic oils can be purchased in a number of different viscosity ratings. The more wear in the wing shaft, the higher the viscosity will be needed. Modern hydraulic oils also have anti foaming additives. The viscosity does change with large temperature changes but that's one of the reasons Houdaille didn't use mineral oil in the early years. The other was the oil affected the seal over time. Glycerin has very little viscosity change with lower temperatures by comparison with mineral oil plus it doesn't foam up easily. It's also an emollient that helps preserve the leather seal. The bad thing about glycerin is the deterioration rate. It has to be replaced more often. Denatured alcohol is about the only thing a person can put in the shocks to clean them out but it all has to come out of there before refilling them.

As the unit wears, higher viscosity fluid will be the only recourse.

[Patrick L.]

I don't understand using glycerin, It was used only for a short period of time before it found to be undesirable.

There are many different weights of hydraulic oils as well as ATF which don't attract/suck water.

[rotorwrench]

Glycerin was the most common of the fluids used by Houdaille but it wasn't the only one. Mineral oil and castor oil were also used. The filler caps had distinct shapes to help the service personnel ID the type of fluid for service. Ford used these type of shocks clear up to mid 1947 when they started production use of piston type tube shocks. The who-dies were throw away units for the most part until production of them ceased.

[Oldbluoval]

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Rotor-
Please elaborate as I’ve rebuilt dozens of shocks and have hundreds (well maybe a hundred!) around here
I’ve never seen anything but the usual square plug
What’s/where’s the difference??

[jw hash]

the V8 shocks used a different filler plug. I`m with Bill on this, I have rebuilt well over 100 of them and i`m setting on over 200 model A Houde, shocks right now. i have never seen any different original plugs.

[rotorwrench]

I was referring to the later units when mentioning the different filler plugs. Model A units were the 2nd in a long succession of who-die shocks used by Ford Motor Co. The Lincoln cars used them back into the early 1920s. Glycerin filled shocks had the flat top filler plug, castor oil filled units had the raised coin shaped cap, and the mineral oil filled units had a raised nipple shape cap but all of this came later in the early 40s.

This link is an interesting study of the shock fluids that used to be available. Most folks would really have no idea what was in the cans of shock oil that they were purchasing back in the day since none of them had any information about what the contents was listed on the cans.
http://www.earlyfordv8clubga.org/Sho...arApr1998).pdf

Ford service bulletins would likely have been the only source of information for the service technicians.

[Kevin in NJ]

I have attached a pdf from one of the A club's articles. It lists the Ford requirements for the fluid.

I also suggest that everyone look up the shock rebuilding and testing in the service bulletins. In particular look at how the shocks are to be tested good.