Allison fluid low

[donaldusmc2003]

Noticed some seepage under the truck. Just a little wet on the side of the transmission by the metal plate. Took to the dealer and they said it wasn't leaking that it was spilt oil from the last change. Ok but how did it get there. No signs of fluid blowing back under the truck and haven't seen any spots in my driveway. Took back today for the brake pedal recall and asked them to check the fluid again. It was 1.5 quarts low and has 40k miles. 2015 Duramax. Question is where could the fluid have gone to?

[Colossus]

have you had the screw on tranny filter changed since you got it? (Assuming the 2015/2016s have the screw on filters like my 08 did) That could be a point of leakage?

[donaldusmc2003]

No filter change yet. Manual calls for it at 45k miles.