Don't know the answer to your question, but having a GMC Savana with a 2.8 Onan, it makes a lot of noise and vibration when running. If I didn't have a generator and wanted to run A/C, I'd just buy a portable unit. Actually I did buy a Honda as well.
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Chris
2008 GMC 3500 Quigley Weldtec 4x4 Savana SMB