I know nothing about motorhomes, however I know the 5.9 Cummins has mechanical valve lifters, and the valves need adjustment periodically. Don't know the interval, but I'd definitely look that up, and stay on top of it. The Allison transmission, if it's like the one used in the GM trucks, has an external spin-on oil filter that needs to be changed when the engine oil gets changed.
Good luck with your motorhome.
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