I have a 1955 M38A1. I believe that somewhere along the line a previous owner swapped out the original tranny/TC for a set from a CJ-5. The reason I say this is the tranny and TC in my military jeep share the same lube. According to the CJ-5 Owners Manual (see below) there can be ports (or drilled holes) between the two components in some CJ-5s. I do not see the same description in the M38A1 manual, which makes me assume this shared lube does not occur in military jeeps.
Every spring, I check the oil level in my tranny and, if necessary, I bring the level up to the bottom of the fill opening. Then, when I go over to check the level in the TC, once the plug is removed oil pours out the hole. So, I quickly reinstall the plug.
The elevation of the plug hole for the TC is slightly below the elevation of the tranny plug hole. I am guessing the TC fill hole is about 1/2" or so lower than the tranny fill hole.
My question is, which is better for my drive train:
(A) Tranny lube at correct level and TC overfilled, or
(B) Tranny lube below correct level and TC at the correct level.