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Do gear oils such as 75W90 sheer down in the same way motor oils do?
Geaer oils sheer?
- Thread starter LoneRanger
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They shear some but they have a lot of EP additives in them to help with the problem. Just think what a gear oil has to go through to survive.
yes even a straight wt will to some degree
Last edited:
MolaKule
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Quote:
Do gear oils such as 75W90 sheer down in the same way motor oils do?
They will shear, but not as badly as other fluids.
EP and AW additives only help to resist wear at the tooth and bearing surfaces.
A properly formulated gear lube will resist shear because of some heavy base oil components such as brightstocks (in the case of mineral oils) or high viscosity PAOs and special polymers (not the VII's), in the case of synthetics, help the formulation to resist base oil shearing.
Do gear oils such as 75W90 sheer down in the same way motor oils do?
They will shear, but not as badly as other fluids.
EP and AW additives only help to resist wear at the tooth and bearing surfaces.
A properly formulated gear lube will resist shear because of some heavy base oil components such as brightstocks (in the case of mineral oils) or high viscosity PAOs and special polymers (not the VII's), in the case of synthetics, help the formulation to resist base oil shearing.
Hi,
Lone Ranger - I have run GL5 75W-90 synthetic gear oils out to 4 years or 1m kms (620k miles) and they were always within the +20% to -20% viscosity range from new lubricant. The range is set by the component Manufacturer
Contamination with water etc and oxidation can be an issue in some applications
Lone Ranger - I have run GL5 75W-90 synthetic gear oils out to 4 years or 1m kms (620k miles) and they were always within the +20% to -20% viscosity range from new lubricant. The range is set by the component Manufacturer
Contamination with water etc and oxidation can be an issue in some applications
Gear oils shear more than engine oils.
But this is because they are being chewed up more. Sliced and diced more. It is rough inside a transmission!
Synthetics are better in this respect.
But this is because they are being chewed up more. Sliced and diced more. It is rough inside a transmission!
Synthetics are better in this respect.
Hi,
mechtech2 - In my 18 speed, triple countershaft, constant mesh (synchro range change) Fuller gearboxes a SAE50 lubricant is specified. A SAE90 EP is often used by the ill-informed!
Using a synthetic SAE50 lubricants and 1m kms (620k miles) OCIs I never saw any shearing at all. In fact in one group of trended used oil analysis (for one vehicle) after 1.07 million kms the viscosity at 40C was 134cSt - VOA is 130cSt.
At that point:
TAN - 3.4
Sodium - 21ppm
Iron - 310ppm
Copper - 65ppm
Lead - 112ppm.
In this case the oil was not changed!
It is true that some differentials and manual gearboxes are harder on their lubricants than others. Manufactures OCIs should be followed unless used oil analysis are used to determine the optimum OCI
mechtech2 - In my 18 speed, triple countershaft, constant mesh (synchro range change) Fuller gearboxes a SAE50 lubricant is specified. A SAE90 EP is often used by the ill-informed!
Using a synthetic SAE50 lubricants and 1m kms (620k miles) OCIs I never saw any shearing at all. In fact in one group of trended used oil analysis (for one vehicle) after 1.07 million kms the viscosity at 40C was 134cSt - VOA is 130cSt.
At that point:
TAN - 3.4
Sodium - 21ppm
Iron - 310ppm
Copper - 65ppm
Lead - 112ppm.
In this case the oil was not changed!
It is true that some differentials and manual gearboxes are harder on their lubricants than others. Manufactures OCIs should be followed unless used oil analysis are used to determine the optimum OCI
Doug Hillary - Yes, but you only have 1,000,000+ on the lube!
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