Well after a couple months lookin in and wishing someone would find the magic cure I guess it's my turn to join in. I feel like going to a meeting and saying "I own a Sierra and yes I have a shake." I special ordered my 2015 SLT crew cab 4x4 with the max tow package. Before I start let me say I also purchased the almost exact same truck a month earlier. The only difference beside the color is it does not have the max tow package. I still have this truck and it does not have a vibration. The max tow truck had 4 miles on it when I got it. It had a vibration during the test drive, I figured it was a tire issue and would work out after a few miles. Talking with my salesman he suggested putting about 2000 miles on it before a tire claim. Looks like a warranty claim before then comes out of GM's money. I agreed, after all my other truck doesn't have a problem, why should this one. Well to shorten the story they went thru 17 tires to find 4 that would road force balance in the 6-7 range. Thumbs up for those great SR-A tires. That was a total of 7 trips to the dealer, requiring me to leave it overnight on 2 occasions. They ended up skinning 2 wheels, which they had to replace. After the tires were in range I still had a shake. Next, according to the pico scope, it is time to replace the ring and pinion, after a re-shim does not work. Truck in the shop 2 weeks before they could find a new set of gears. After the gear swap the tech working on it says it didn't change it at all. Truck still in the shop, 3 weeks and counting. They are still trying to find the problem. Truck now has 4900 miles. I told them I would give them until Friday before I started the BBB process. Really hope they can fix it, after all I special ordered it wanted it. If I have to replace it that means another 8 weeks for a special order, and it will not be another GM product.