New to the site but I have the same problem with my Sierra Crew Cab SLE 4WD that started at about 400 miles so it did not come out that way, and as for as the comments take it back to the dealer they will fix it, the LEMON Law, give it back to the dealer, that is all a crock of you know what, I have had my truck back the dealership 8 times for the same problem a vibration, they have had the factory engineers out three time and looked and worked on it, first time the engineer did a couple of things and said that it was up to factory specs and that was all he could do, I drove it home and before I was a block away I could tell that they did not fix it, when I got home I called the dealer back and told him so he called GM and the next week they sent out the same guy and this time he worked on 5 or 6 other things that he did not work on the first time after telling me they did all they could do the first time. Right there tells you they are lying if there was nothing they could do why come back and work on it again! But after he got done it was just like it was, I will try to list some of the stuff that they said they did, 1) rotated the tires 2) re-torque the wheels 3) balanced the tires 4) balanced the drive shaft 5) shimmed the rear end 6) checked the rear shocks 7) took off dealer installed MUD FLAPS! 8) checked the exhaust system, I know but they did 9) road forced tested the tires twice and replaced two the second time and re-balanced the tires. And I'm sure I have not listed all they have tried, and still I have the same problem, third time the engineer came out he had the regional manager with him and this time they drove my truck and 2 others they had on the lot and said that they are similar to mine and they was not going to do any more to my truck that they had done all they could or would do but if I had any other problems to bring it back. I filed a claim with BBB Auto Line and after all the times back to the dealership with no Joy they said I could go before an Arbitrator but more than likely because this was not a safety issue are it had not been out of services for long periods of time that the outcome would probably not be good. So I know now that after posting this I have as much hope in one of the readers fixing my truck as GM and that is sad that they just don't care anymore. I have been a long time customer of GM cars and trucks owning over 11 GM truck in the past 30 years. P.S. have the dealer buy it back tired that too he said he would buy it back and give me $32,000.00 for the truck that sticker ed for $46,000.00 because "wait for it",,,, because it had a vibrations in it !