Lubricants

To quote George Teebay: Transmission & Rear End Oil: P-A [the company] only provided owners with the push-type heavy-liquid-dispensing grease gun, called, ‘compressor, grease’ in the owner’s manual. Because of the frequency of required lube, they assumed that much of the routine lubrication would be done by owners. That heavy liquid was ‘Special Compound,’ which was their proprietary name for 600W.

I use 600W ONLY for the transmission and the steering box. (You should also use 600W for the Bowen auto-lube system.) I do NOT use the push-type gun for any of them–especially not for the steering box because you can still blow out seals with that. Heat a bottle in a pan of near-boiling water then pour using a small-aperture funnel. I’d prefer to use the 600W from a Model A Ford supplier for all 600W applications other than the transmission–but make sure you’re getting the dark, smelly, viscous 600W and not the clearer, thinner stuff some sell as 600W but which I think is just repackaged SAE 140.

Differential: They did not have hypoid-style gear oils in 1928 (but they were close to it at that time), which is STRONGLY PREFERRED these days for the differential. As far as I know, SAE 140 hypoid-style gear oil is about as heavy as hypoid oil as we can find nowadays–but be sure to USE ONLY GL-4 rated, not synthetic (GL-6) or the now-common GL-5 which is for limited-slip diffs.