Differential Oil

[CatMan1]

I can't seem to find this anywhere. In my '26 what should I be using for differential oil/grease? Maybe 600WT?

 

[stevests]

Go to a good auto parts store and get a jug of 140 wt. - G4 - should have posted GL4.

 

[J Franklin]

Go to a good auto parts store and get a jug of 140 wt. - G4.

And if you want add some STP additive to make it more sticky.

 

[40 Deluxe]

And if you want add some STP additive to make it more sticky.

But why do you it "sticky"??

 

[J Franklin]

Since these cars are not everyday drivers, it sticks to the gears and bearings stopping corrosion.

 

[rotorwrench]

SAE 140 gear oil is already pretty sticky. STP oil additive is a viscosity builder. It will add viscosity to what ever it is added to. 600W steam cylinder oild was not an SAE rating. The modern equivalent in viscosity is SAE 140 gear lube.

For a model T with low speed use and relatively light payload, a GL1 type gear lube can be used. GL4 should be OK too since is is low in extra pressure additives. Old original axles may still have babbitt thrust washers in the side bearing assemblies. It is advisable to replace these with bronze or brass washers that are currently available. This soft or yellow metal component is the reason that GL5 type gear oils should be avoided due to the higher concentration of extra pressure additives.