Oil in bell housing ??

[Doe69936]

Is there supposed to be motor oil draining from the plug in the attached photo?
Looks to me like the bell housing and I can't imagine why there would be motor oil in there unless I have a massive rear main seal leak
The bus is a 2005 thomas safetliner 8.3 Cummins and I believe the transmission is an Allison 2000

[Jolly Roger bus 223]

Make sure it's oil and not dirty/grimey tranny fluid.
Hate to pull all apart and replace the rear main put it all back together and find it was the tranny seal.
But if I had the tranny out for any reason it would get front and rear seals anyway.
But it would suck to replace the rear main it wasn't leaking and find out you only had to slide the tranny back a foot to replace the front pump seal

[Doe69936]

Definitely motor oil but yeah I'll do both when I pull it just for good measure
Now I'll habe to measure my oil loss rate and see when I'll have to pull it thank you