85/90 Weight vs Hydraulic Fluid

[Bob64]

There is a small but important gear box on my 3PtH snow blower (about 30 years old) that has started seeping oil. Without a garage or nice workshop I don't want to change the seals in the middle of winter (7 deg. below this a.m.) With that said I plan to just add gear lubricant as needed, checking the level prior to snow blowing. Depending on how good a job I want to do I can spend one to two hours blowing the snow and more if I do my neighbors also.
My question is: I currently don't have any gear oil on hand so would it be okay to use hydraulic fluid instead of the 85/90 weight gear oil? I have a couple gallons of leftover hydraulic fluid from when I changed it on my Kubota tractor. Since Kubota uses hf in their gear boxes I would think it should be fine. Before I do however thought I would like to hear opinions from this forum. I've attached some pictures

 

[Eagle1]

My theory is that any oil is better than no oil. That said I would expect 80/90 to provide better gear protection than hydraulic oil, reason I prefer to run that in front axles over hydraulic oil.

Still would think that any lubricant is better than none. YMMV

 

[RjCorazza]

I prefer gear oil in front axles that allow HST fluid as an option. I personally would not use HST fluid in a gear box period.
For a leaking seal your could use a 75w140 in your blower, or corn head grease.

 

[paulsharvey]

So, if its already leaking, some hydraulic would be OK for a use or two, and it will quickly self drain. Maybe by the next time, you'll have some Cotton Picker, pourable grease to fill it with.

Just keep in mind, it had gear oil, and leaked empty, hydraulic will leak out 4 times faster... So, go ahead and place the Amazon order, but fill it up for now.

 

[4570Man]

If the hydraulic oil stayed in the box I doubt you’d have any problems. But the hydraulic oil is considerably thinner and it’s already leaking. I wouldn’t use it.

 

[ray66v]

Most hydraulic oil is not in fact, considerably thinner than 80-90w gear oil.

Hydraulic oil is measured on the motor oil scale, and gear oil has a completely different scale.

The viscosity of most hydraulic oil is about 30w, and that is about the same viscosity, at normal temps as 80w gear oil.

There are exceptions like, the Kabota hydraulic oil that is closer to 20w.

And, every brand of oil has a slightly different viscosity, even when it is sold as the same weight.

But, hydraulic transmission oil has to be able to protect gears. And, the two are interchangeable in many applications. The difference is the additives chosen for a given application.

 

[Bob64]

I want to thank everyone for your quick responses. Now that I have a better understanding of the viscosity ratings I will wait until I go into town & pick up heavier gear oil. Hopefully no big snow storms between now and then.

 

[Rvrrat14]

I’ve found on my 51 Willys Jeep using later multi-vis gear oil leaks by old seal/machining, even if sealed with ‘goop’.
After searching I found TSC keeps ‘Ford Tractor Oil’, which is simply straight 90 wt mineral oil. Older equipment needs this stuff and leaks have stopped.