TexAXis, I think you'll find it's an industry-wide practice because RV manufacturers start the new model year around February or March, whereas Ford may not change model year until around May or so -- that date seems to vary depending on how much they are updating chassis.
In case of Axis the chassis has to get reworked at MorRyde so by the time it gets to Thor and motorhome is built, I'd assume more than half of them were built on different model years -- chassis versus house.
I can provide the link to Ford specs if you want to compare for yourself, but as I stated before, I don't recall any real change between 2016 and 2017 for the E-450 chassis.
The next big chassis change "may" be when Ford goes to V8 as an option to V10, but I think even that is unlikely to make it into Axis/Vegas line.
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