check the cooling fan blades, see if maybe one is cracked, bent or broken or if the shroud is broken any of those would make the fans make excessive noise or vibration especially under a load. use a flashlight and look closely and carefully.
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Must've been the cough syrup!So I have a 2008 Denali and when the HVAC power button is on it roars when accelerating until it hits high gear and goes away. This only happens when HVAC button is on, if it's off it accelerates with no noise at all. Need all the help I can get.
I later figured out that my passenger side motor mount was broken and anytime under a load it would roar and then quiet down once it shifts to high gear. The motor mount was the culprit!So I have a 2008 Denali and when the HVAC power button is on it roars when accelerating until it hits high gear and goes away. This only happens when HVAC button is on, if it's off it accelerates with no noise at all. Need all the help I can get.
Recommend you go back to start of this thread and and edit the title to say SOLVED and that alerts others to look thru this post for a fix.I later figured out that my passenger side motor mount was broken and anytime under a load it would roar and then quiet down once it shifts to high gear. The motor mount was the culprit!