Reducing gearbox oil

[jenevers]

my manual issue (44.1) says" use an extreme pressure heavy gear oil of MINERAL base. But mine has SYNTHETIC 75W-90 (API GL-5). Will that be OK?

[Flyboy]

I think you may have answered your own question. Stick to the oil recommended by the gearbox maker. There are corrosion issues with some gear oils where gearboxes contain yellow metal parts.

[jenevers]

I think you may have answered your own question. Stick to the oil recommended by the gearbox maker. There are corrosion issues with some gear oils where gearboxes contain yellow metal parts.

Hmm. Well I wonder if synthetic oils were around in 1945 when my gearbox was built. Reading this

 

http://www.machinerylubrication.com/Read/167/synthetic-gear-oil

 

 

tends to make me feel that synthetics are probably better than mineral oils.

 

I know what the manual recommends...... But it also recommends changing the oil every 4 months!!!!!

And, is there any yellow metal in a 2UC reducing gear?

Edited March 23, 2015 by jenevers

[PeterG]

So I would say the two things I think could cause you problem with a synthetic oil is if water gets into the oil which can then cause corrosion or a bad reaction with some of the component parts which make them degrade.

 

On the balance I would say if you can use the recommended oil why do you need to change and take the risk of the potential side effects causing you a problem.

 

The changing the oil every 4 months would only be for a very heavy set of operating conditions which you would not have a chance of seeing so can be forgotten.

[swift1894]

So I would say the two things I think could cause you problem with a synthetic oil is if water gets into the oil which can then cause corrosion or a bad reaction with some of the component parts which make them degrade.

 

On the balance I would say if you can use the recommended oil why do you need to change and take the risk of the potential side effects causing you a problem.

 

The changing the oil every 4 months would only be for a very heavy set of operating conditions which you would not have a chance of seeing so can be forgotten.

But wouldn't water getting into a mineral oil be just as bad?

The manual states " if there is any indication that water may have entered the gear case, immediately drain and flush out repeatedly with oil until all traces of water have been removed".

Edited March 25, 2015 by swift1894

[PeterG]

No in synthetic oils the water gets chemically bonded which reduces the lubricating ability of these oils under loads seen in gearboxes such as this, unlike the traditional (old fashioned) petroleum based oils which do not chemically bond with the water. This is not seen in engines as the loading is of a different type and hence why you do not run an engine on an EP oil.

[swift1894]

No in synthetic oils the water gets chemically bonded which reduces the lubricating ability of these oils under loads seen in gearboxes such as this, unlike the traditional (old fashioned) petroleum based oils which do not chemically bond with the water. This is not seen in engines as the loading is of a different type and hence why you do not run an engine on an EP oil.

Thanks for the info. All interesting stuff. Synthetic drained and replaced with mineral based oil!

Edited March 31, 2015 by swift1894