Your Itasca 40U most likely has a HWH leveling system, which has a manual dump switch for the air bags. It also dumps the air bags when you select automatic-leveling. You will find a link to HWH (and owners manual) in a sticky on the Winnebago forum.
Your MH is quite similar to D Lindy's I suspect. You do have your motorhome listed, just 2 clicks away from here, good job! And welcome to irv2.com
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2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA.
" My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy