Rag top fluid

Discussion in 'Paint and Body' started by chromebumpers, Jul 5, 2018.

  1. chromebumpers

    chromebumpers solid fixture here in the forum Staff Member

    For my 1968 Catalina convertible, My top is too slow and it’s a new pump. What fluid is used for the hydraulic pump and how do I get to it?
  2. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Its Dextron ATF.
    You could use Universal Tractor hydraulic fluid too.
  3. chromebumpers

    chromebumpers solid fixture here in the forum Staff Member

    Good, I don’t have to buy anything else - have enough of that in stock.
    Thanks Brian!
  4. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member


    How Do You Know if You're Using the Right Hydraulic Oil?
    Stephen Sumerlin, Noria Corporation
    Tags: hydraulics, industrial lubricants
    For most lubricated machines, there are many options when it comes to lubricant selection. Just because a machine will run with a particular product doesn’t mean that product is optimum for the application. Most lubricant misspecifications don’t lead to sudden and catastrophic failure; rather, a misspecification shortens the average life of the lubricated components and, thus, goes unnoticed.

    With hydraulics, there are two primary considerations – the viscosity grade and the hydraulic oil type (AW or R&O). These specifications are typically determined by the type of hydraulic pump employed in the system, the operating temperature and the system’s operating pressure. Selecting the best product for your system requires that you collect and utilize all available information.

    Hydraulic Fluid
    Hydraulic fluid has many roles in the smooth operation of a well-balanced and designed system. These roles range from a heat transfer medium, a power transfer medium and a lubrication medium. The chemical makeup of a hydraulic fluid can take many forms when selecting it for specific applications. It can range from full synthetic (to handle drastic temperature and pressure swings) to water-based fluids (used in applications where there is a risk of fire).

    A synthetic fluid is a manmade chain of molecules that are precisely arranged to provide excellent fluid stability, lubricity and other performance-enhancing characteristics. These fluids are great choices where high or low temperatures are present and/or high pressures are required. There are some disadvantages to these fluids, including high cost, toxicity and potential incompatibility with certain seal materials.

    A petroleum fluid is a more common fluid and is made from refining crude to a desired level to achieve better lubricant performance with the inclusion of additives, which range from anti-wear (AW), rust and oxidation inhibitors (RO) and viscosity index (VI) improvers. These fluids offer a lower-cost alternative to synthetics and can be very comparable in performance when certain additive packages are included.

    Water-based fluids are the least common of the fluid types. These fluids are typically needed where there is a high probability of fire. They are more expensive than petroleum but less expensive than synthetics. While they offer good protection for fire, they do lack on wear protection abilities.


    Figure 1. Viscosity Selection for Hydraulic Fluids

    Pumps and Viscosity Requirements
    There are three major design types of pumps used in hydraulic systems: vane, piston and gear (internal and external), and each of these pump designs are deployed for certain performance tasks and operations. Each pump type must be treated on a case-by-case basis for lubricant selection.

    Vane: The design of a vane pump is exactly what its name depicts. Inside the pump, there are rotors with slots mounted to a shaft that is spinning eccentrically to a cam ring. As the rotors and vanes spin within the ring, the vanes become worn due to the internal contact between the two contacting surfaces.

    For this reason, these pumps are typically more expensive to maintain, but they are very good at maintaining steady flow. Vane pumps typically require a viscosity range of 14 to 160 centistokes (cSt) at operating temperatures.
  5. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    There are other articles I read on Hydraulic fluid.
    What is used in Modern Farm Tractors is Superior.
    Plenty of Film strength for Hypoid Ring and pinion gearsets.
    Share the same resevoir as the Hydraulics, Transmission, and Diff.

    Then there is Jet Turbine oil.
    Some guys use in place of ATF.
  6. chromebumpers

    chromebumpers solid fixture here in the forum Staff Member

    So what type of pump is used on GM convertible tops from the ‘60’s?
  7. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    I am not sure.
    Been a long time.
    The C4 Corvette has a manual Top.

    Likely made By Declo Moraine on your 68 Cat.

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