Which Trans and Rear End Oil?

What would you guys run in a 1939 Ford transmission and a stock 1932 banjo rear end? 90 weight or 140?

 

Not synthetic

 

There were changing recs over the years as grades and additives changed...
Safe would be 140 for hot weather, all the time if leaky or worn parts, 90 winter, would be fine all the time if everything in good shape. Original '32 grade was something odd and obsolete now, 220 or so, Ford changed specs retroactively to the above.

 

90 is good for winter, but in warm weather, 140 is better. Lubrication Engineers is good stuff. You can get it from Speedway. Mobil still makes 600W. Probably have to locate a distributor to find it though. They make some that's heavier than 140, but that's usually special order.