: I have an full-sized 1997 International 3800 with DT466e and Alison 4-speed auto transmission.
I was crawling around yesterday underneath and noticed a hole in the center of the trans (see arrow in pic). It is particularly weird because I can see gear teeth through that hole, and I know mud/water never belongs around gears.
I thought I was missing a drain plug or something, but the hole is NOT
threaded. In fact, it is kind of rounded actually. There is some oil residue around it, but I have no idea what kind of piece would cover that hole at all other than like a rubber stopper plug which I've never seen on any engine ever.
Any insight as to what this is?