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rotorwrench · 01-22-2024, 07:22 PM

The SAE gear oil viscosity grading came out before Ford finally changed away from 600W Steam Cylinder Oil. Henry worked in Locomotive shops in his early days and change wan't something that came easy to him.

The 1500 mentioned appears to be the later ISO international standard. ISO-1500 is at the top of the list when compared to SAE which puts it at the top of the SAE-250 gear oil viscosity range. 600W was not quite that thickness of viscosity, It compared more to the SAE-140 to SAE-190 range so it's not quite as thick as the ISO-1500.

When Ford went to the synchronized transmission in 1932, they changed to SAE-80 winter and SAE-90 summer but it is a synchro type unit. The spur and dog unit of the model A can use a more viscous lubricant but a lot has to do with how well a person can match rpms during a shift up and especially during a down shift attempt. The engine rpm versus main shaft rpm have to be pretty close to get the gears to slide in like they should.

01-22-2024, 07:22 PM	#12
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,462	Re: Grinding The SAE gear oil viscosity grading came out before Ford finally changed away from 600W Steam Cylinder Oil. Henry worked in Locomotive shops in his early days and change wan't something that came easy to him. The 1500 mentioned appears to be the later ISO international standard. ISO-1500 is at the top of the list when compared to SAE which puts it at the top of the SAE-250 gear oil viscosity range. 600W was not quite that thickness of viscosity, It compared more to the SAE-140 to SAE-190 range so it's not quite as thick as the ISO-1500. When Ford went to the synchronized transmission in 1932, they changed to SAE-80 winter and SAE-90 summer but it is a synchro type unit. The spur and dog unit of the model A can use a more viscous lubricant but a lot has to do with how well a person can match rpms during a shift up and especially during a down shift attempt. The engine rpm versus main shaft rpm have to be pretty close to get the gears to slide in like they should.