Read the 100s of comments here about gm leaving customers in the dark and offering no help. You got lucky. GM 4 years ago is different the GM now. But they were a nightmare to me on my 2016 as well as my 19
My 16 Silverado was a shaker. 7 times at the dealer. They did EVERYTHING to try and fix it. I was polite, kind and patient and it still got me no where. GM finally told myself and dealer there is nothing more they can do and the truck is operating fine. my shake was so bad that it would spill whatever drink you had in the center console cup holder. The dealer felt super bad as one of my friends was the service advisor. GM simple would not do anything else.