Hi all!
There's a post a bit below here concerning hydraulic fluid for hydrostatic transaxles. My question is similar, but different: TuffTorq, one of the largest manufacturers of self-contained hydro transaxles says to use 5W-50 synthetic motor oil for refill purposes in the Knnaa series, at least. (Ironically, new units for many tractor manufacturers apparently come with mineral oil from TT). I'm trying to understand why they'd recommend motor oil in this application. Not to say that they don't know what they're doing, but still... Seems to me that a synthetic hypoid gear oil of the same approximate viscosity as the 5W-50 would be a viable alternative, no? For what reason would they want to use something with additives designed for an internal combustion engine, in an application that's for all intents and purposes, sealed? We already know that the gear tooth pressures in the differential are typically high enough to cause pretty consistent spalling. Is it possible that motor oil performance would be better than gear oil?
Additionally, one of the classic problems that these things seem to have is viscosity change with temperature: "My tractor doesn't work when it's warmed up." Wouldn't a gear oil present better viscosity stability with temperature?
I'm confused. What could be going on here?
There's a post a bit below here concerning hydraulic fluid for hydrostatic transaxles. My question is similar, but different: TuffTorq, one of the largest manufacturers of self-contained hydro transaxles says to use 5W-50 synthetic motor oil for refill purposes in the Knnaa series, at least. (Ironically, new units for many tractor manufacturers apparently come with mineral oil from TT). I'm trying to understand why they'd recommend motor oil in this application. Not to say that they don't know what they're doing, but still... Seems to me that a synthetic hypoid gear oil of the same approximate viscosity as the 5W-50 would be a viable alternative, no? For what reason would they want to use something with additives designed for an internal combustion engine, in an application that's for all intents and purposes, sealed? We already know that the gear tooth pressures in the differential are typically high enough to cause pretty consistent spalling. Is it possible that motor oil performance would be better than gear oil?
Additionally, one of the classic problems that these things seem to have is viscosity change with temperature: "My tractor doesn't work when it's warmed up." Wouldn't a gear oil present better viscosity stability with temperature?
I'm confused. What could be going on here?