3 times to dealer same problem my v6 engine vibrates in park can feel it in my seat, center console shakes real bad at 77 mph, so I called gm 1-800-462-8782 . they say its in there specs from the engineer's can't trade in for 6 months [gm discount] really a brand new truck that vibrates? 3 new gm vehicles in the last 4 years looks like my last! 71-1389123829 is my Complaint no. thanks Sapaugh dealership 636-931-0055 in Herky, Missouri for selling me a lemon, ps sold my extended warranty in at 45 days, if they can't fix it why have one .