What is the ideal manual gear box oil temperature?

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ptuomov
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What is the ideal manual gear box oil temperature?

Post by ptuomov » Sun Aug 26, 2018 11:52 am

What is the ideal manual gear box oil temperature? Any data on this, or oil company or gearbox manufacturer recommendations?
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU

Kevin Johnson
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Re: What is the ideal manual gear box oil temperature?

Post by Kevin Johnson » Sun Aug 26, 2018 12:22 pm

http://www.eaton.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/tcmt0021en-us.pdf wrote:Operating Temperatures/Cooling
Requirements
Transmissions must not be operated at temperatures above
250 °F (121 °C). Operation at temperatures above 250 °F
(121 °C) causes loaded gear teeth temperatures to exceed
350 °F (177 °C) which will ultimately lead to premature gear
failure.
If the elevated temperature is associated with an
unusual operating condition that will recur, a transmission oil
cooler must be added, or the capacity of an existing cooling
system increased.
The following conditions, in any combination, can cause
operating temperatures of over 250 °F (120 °C):
• Operating consistently at high/low speeds
• High ambient temperatures
• High horsepower operation
• Restricted airflow around transmission
• Excessive use of engine retarder
• Exhaust system proximity to transmission
• High power PTO operation for extensive periods
while stationary
• High engine RPM for extensive periods
External oil coolers are available to reduce operating
temperatures when the above conditions are encountered.
Eaton oil cooler systems must meet a minimum requirement
of 3/4" water coolant lines and 8 GPM water coolant flow at
1500 RPM. The end user is ultimately responsible for
maintaining transmission lube temperatures below 250 °F
(121 °C). Transmission oil coolers must be used to reduce
operating temperatures when the above conditions are
encountered.

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Re: What is the ideal manual gear box oil temperature?

Post by ptuomov » Sun Aug 26, 2018 12:48 pm

And 4340 steel melts at 2600F. However, what’s the ideal temperature for gearbox oil in the sump?
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU

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Re: What is the ideal manual gear box oil temperature?

Post by Kevin Johnson » Sun Aug 26, 2018 1:14 pm

TRTS0910_1007.pdf wrote:In most cases normal operating temperature is approximately 100°F. (40°C.) above ambient.
Since you and Mr. Kuhn are developing a new application it is up to you to decide on an optimal temperature and then regulate it.

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Re: What is the ideal manual gear box oil temperature?

Post by ptuomov » Sun Aug 26, 2018 2:11 pm

To repeat what I posted in another thread, my current thinking is the following:

Water in the oil will cause hydrogen embrittlement or rather hydrogen assisted cracking in the case of steel. To get rid of any water in oil, the transmission oil needs to be above minimum temperature and the transmissions needs an effective breather. The temperature of the tranny oil increases by about 50-100F when it runs thru the gears, so the minimum safe temperature for transmission oil is somewhere between 110-160F in the sump. From those temperatures, the oil between gears heats enough to boil out any water (and assuming the gear box is vented, get rid of i).

On the other hand, various manufacturers seem to say that the gearbox oil in the sump should never go over 250F. If you say that the gears then heat that by about 50-100F, that would mean 350F for the oil. That would lead to breakdown of most oils, no? So I'd say that maximum allowed temp should be about 230F in the sump, targeting maximum of 330F under pressure and assuming the worst case +100F increase in those conditions.

Based on this logic, one should look for 160-230F temperature for transmission oil in the sump. And if I am using an external oil cooler with a thermostat, the usual thermostats seem to turn the cooler on at 180F, which is in that range.
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Re: What is the ideal manual gear box oil temperature?

Post by ijames » Sun Aug 26, 2018 3:34 pm

Perhaps coat the gears with WS2, or use an oil with some? It would lower the friction and also serve as a hydrogen barrier to slow uptake from any water that might be in the oil, especially if you are concerned that you aren't heating it enough to keep it dry. A quick google search found this as a starting point: http://pubs.rsc.org/en/Content/ArticleL ... ivAbstract.
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Re: What is the ideal manual gear box oil temperature?

Post by Keith Morganstein » Wed Aug 29, 2018 6:03 pm

ptuomov wrote:
Sun Aug 26, 2018 12:48 pm
And 4340 steel melts at 2600F. However, what’s the ideal temperature for gearbox oil in the sump?
I think the point is at over 250* Oil temp, failures dramatically increase. It’s imminent failure by 350* ( the oil is done)


140* to 160* F is where you want it.
Automotive Machining, cylinder head rebuilding, engine building. Can't seem to quit #-o

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Re: What is the ideal manual gear box oil temperature?

Post by ptuomov » Wed Aug 29, 2018 6:11 pm

Keith Morganstein wrote:
Wed Aug 29, 2018 6:03 pm
140* to 160* F is where you want it.
And no concerns about not boiling the condensation water out of the fluid if one (theoretically) can keep the oil at such a low temperature?
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU

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