SAE 80 EP ?

It will work fine

EP stood for Extra Pressure, hence to make sure there was still a film of oil between the gear teeth from the torque. Due to the oil chemistry we have today there are additives that eliminate this designation. Todays 80/90 weight is the replacement.

Just got my hands onto my fathers D17. It rarely gets used, and will basically be a "tinker toy" for me to fix up, and rejuvenate... Getting ready to drain and replace fluids. Opinions on synthetic fluids instead of conventional? It will probably get less than a few hundred hours a year unless I roger up for the elder farmers around here. And even then it won't be many hours.

I just did this when servicing planetary finals on the rwa axle on my combine. Manufacture wanted 90ep, can't find that product anywhere. Google search says Castrol makes it; appears to be readily available in Europe, not in continental US. Ok, so what to use as a substitute? I used Scheiffer's 75w90 synthetic. I recommend you use a synthetic also.

Here's the deal, 80w90 has additives. Those additives are designated on your container as API rating (GL5, GL4,....ect) API GL5 meets military spec. Each rating refers to the additives in that particular oil. Problem with additives some are corrosive, caustic, to yellow metals (brass, bronze, ect....) I can't say because I haven't had a D19 rear end apart, nor have I broken into the finals on my rear wheel assist, so I can't say that there are yellow metal shims or whatever inside the gear case. Nor do I want to find out with the expense of replacing. Part of the "engineering" in synthetic oils is uniform molecule size, as well chemical make up not needing additives.

Like I was saying I went with a synthetic and feel safe with it. I saw this thread and thought I might chime in, certainly not an expert, just recently went through the same process as you.

Hope this helps

You may run in to a leak horse. Synthetic oils will come in and clean out sludge and seals and 'relax' them. Unless overhauled with new seals, I do not recommend it. I have been in heavy equipment for 20 years and have seen this happen several times- automotive and off road

Look I am a firm believer in synthetics. But I do not and will not run it in anything pre 1988 unless overhauled (automotive). They will leak! And I found it to be true that Engines & Transmissions designed to take straight weight oils do not like multi viscosity fluids and have found evidence with bearing failure due to oil break down and overheat.

I wish not to upset anyone but I have spent many years replying to the questions and comments label and or calling the phone numbers on the back of products to receive more information. I'm kind of a dork when it comes to fluid analysis. More expensive generally doesn't mean better in fact the oil that Tractor Supply sells is the same quality as high end brands.

Everybody has their own preference and 'doctored up 'mixture to feel good about, even myself. I have always felt if you need to add something to your oil to get it to run right, you are prolonging a problem. There are additives to help cool oil and add lubricity and that's great. But we all know that these machines have been in service way longer and have way more bearing wear than what a little bit is synthetic additive will help now!

And then you will get leaks anyway DougS

Common leak problems with the synthetic oils is the use of permatex instead of a proper gasket. The synthetic oil will eat the blue goo and cause a leak.

Even in the 40's and 50's they had what we called detergent oil.  We found in machines that had not been recently overhauled that using detergent oil could cause leaking and oil burning.  It took the crud away that kept the oil from burning or leaks.  Got quite a few more hours on the engine till overhaul.

Just curious, I have a 1963 D-19, the AGCO salesman sold me the GL4 (AGCO brand) multi for the power director and hydraulic , it states semi synthetic, he said it would be safe for my tractor, but I should still use the 80-90 in the final drives, , what's you opinion on that, Thank You, Pete

MACK wrote: Put hydraulic wet brake -821-universal hydraulic. Don't use that heavy stuff that don't get in bearings in cold weather.   MACK

exactly what I did with my D19 twenty-six years ago and no problems and in the early 90's it was my heavy tillage tractor. That is what 190's eventually went to and it's the same basic transmission as a D19. 7000's too.

821 is a universal tractor hydraulic fluid. 90 weight will destroy that power director in the cold and make the tractor creep even out of gear. Most stores list what you need as tractor hydraulic fluid, TCH or THL.

Leaks are guaranteed on relaxed seals and usually in older equipment. It's not something to throw the flag up and walk away from. That's just the way it is. Fix the problem or problems and you're fine. It's just something that you have to deal with with older equipment.