I thought that they were built to run ATF, Allison recommends ATF, and the military used SAE10 motor oil just to simplify their logistics.
Hello, Mark. Born and raised in Corona. Left after grad from HS in 64; never come back except for reunions. Anyway, I wanted to draw attention to your "find" of the piping plumbed into the intake behind the filter canister. I suspect one of these is a transmission vent. As noted, after a recent trip I found motor oil in the filter canister, and next found that the tranny had been significantly overfilled.
Do you think the overfill could be responsible for the oil in the filter canister? I suspect another tube is a TC vent, but I really don't know yet where any of these pipes go. Oil smells fine; not burned. Definitely not crank case oil (too clean).
Do you know where the plumbing you found, which is the same that I am curious about, travels to? Regarding transmission fluid filters, someone told me that this Allison does not have an internal filter, in the pan. They said that the external screw on filter is the only one. He is not a Steel Soldier, though and is not familiar with these trucks.
So, my next question is "If I change fluids is there another transmission filter in the transmission itself, like we see with cars?" I suspect there is, but am not certain. I have lots of HS friends that live in Riverside. Mostly VN buddies. A retired Riverside police officer, now quadriplegic, one of my best friends. Served his country honorably. Most of my VN buddies came back in bags, though; one, from Norco, with a posthumously awarded Medal of Honor. George Allen Ingalls. Sorry, getting off track. Just an old tired man reminiscing. Thanks for your help.