In Reply to: hydraulic fluid or Gear oil posted by Gayla Stahl on May 08, 2017 at 18:18:38:
When the lift system acts squirrely like that, you have issues internally, not necessarily the wrong oil. I suggest you R&R the hydraulic system thoroughly, starting with condition of oil -is it diluted with water? If it is a murky brown color then yes it is contaminated and I further suggest you don't use the lift at all until you fix it. You can go the archives here and plug in any keyword(s) to get multiple old replies/posts to your questions. We also have a ton of DIY PM projects to do as well in our HOW-TO's forum. Meantime, here is a LINK to some info on HISTORY forum about the Ford Hydraulic oil. Also, here are some words from a member here, TOH (The Old Hokie) on hydraulic oil...
"...The Ford tractor oil sold at TSC is nothing more than SAE 90 GL-1 gear oil. That is as generic as it gets and about the lowest performing gear oil you can buy today. The N-series owner's manual specifies M4864A/B tractor oil. That was the 1940 Ford specification for industry standard SAE 80 a 90 mild EP gear oil. In the current world that would be most nearly approximated by a GL4 gear oil. Putting "specially formulated for old Ford tractors" on the label of the generic GL-1 gear oil is nothing more than marketing hype aimed at people who will believe anything they see on a label. It is the lowest performing gear oil you could possibly choose for your tractor and not what Ford recommended during N-series production.
As I said before - in today's world there is nothing special about the 50+ year old M2C-134D specification or the Ambra Multi-G 134 oil that CNH was selling. That specification is just an old OEM specification for what is now industry standard and inexpensive Universal Tractor Transmission Fluid (UTTF). Kubota has one they call UDT, JD has HyGard, and CNH now has HyTran which is their newest formulation that replaces MasterTran and Multi-G 134 in most of their applications. They are all virtually identical UTTF products. Fundamentally UTTF is nothing more than a high viscosity index, mild EP, SAE 80 grade gear oil with GL-4 level performance.
In some specific "state of the art" type applications the OEM formulations are very carefully tailored to the peculiar friction requirements of the OEM design and generic formulations may not provide the same level of performance. Limited slip differentials, viscous drives, and hydrostatic and synchromesh manual transmissions are some examples of where the OEM oils MAY be a better choice. A 60+ year old N-series tractor is not one of those applications.
In a nutshell my recommendation is use any good quality UTTF, avoid low end UTTF's (the "303" branded stuff in particular), and if you want to use a gear oil avoid mono-grade GL-1 oil and use a mild EP multi-grade formulation with GL4/GL5 level performance.