Ok, I can't remember what oil goes in the 203 and what is the oil capacity.
I want to say 30W motor oil, but not sure if 10W30 or 10W40 would be preferred.
Also 7 quarts sounds right, but don't remember.
It is supposed to be straight 30w non detergent oil. You can use straight 20w in winter. You do not want to use a multi vis detergent oil which will not lube it as well and tends to foam up in case too! (non detergent oil will not foam)
I've seen both use, I've actually seen people use 90W and sware that's what is suposed to be used, but it is 9 quarts of 30W right?
Yes or until it runs out of fill plug. I cannot varify capacity in manuals here but I can varify the 30w. I am thinking closer to 7 quarts though. I was driving when they first came out and remember that Tcase well!!
I've seen on a shop manual and it's calling out 50w on t-case.
The manuals are in error. I remember when those things were new. New Process (who made the case for Ford, GM, Dodge and IH) spec'd it for striaght 30W non detergent oil in summer and you can use striaght 20 in winter if it gets below zero a lot. DO NOT USE MUILT VIS OIL regardless of what manuals may say as it lasts the longest with regular changes of non detergent oil which does not foam like muiltvis oil can do with the high chain speeds at times in that Tcase. All of those engine additives in modern muilty vis oil are of no value to keeping your Tcase alive.