Dodge shop manual calls SAE 90 oil for the transmission lubricant.
B&W R10 manual recommends SAE40 straight motor oil for the OD unit lubricant.
In the Mopar 3-speed+R10 unit, do the lubricants mix - aren't the OD and 3-speed sealed in between?
R10 manual allows heavy oil for extreme heat, but here in north those conditions do not exist.
Does a heavy oil hinder the OD from working as quick as required?
Would like to learn what do you use in your units?
Experiences using different weight oils?