Three weeks ago I decided to retire my 2008 Sierra and sign the papers on a new one. I picked up a 2014 GMC sierra SLT 4X4. I have noticed a really annoying vibration during low cruising speeds (30-40mph) when the truck goes into v4 mode. I have taken into the dealer and they say that it is the normal operation of fuel management system, and it is because the exaust sytem is detuned while only firing on four cylinders. Has anyone heard of this theory? I am so disapionted right now and ready to sell it. Frustrated I guess since my 08 had a vibration that I could not get rid of at 60-70mph.
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