DCon

BTW . I have owned 2 other GM trucks in the past. A 2004 Silverado Ext Cab Z71 4x4 5.3L , bought from my uncle at 35K miles. Then traded it for a (NEW) 2007 Silverado Ext Cab Z71 5.3L 4x4, neither of which had any vibration problems. I have noticed the vibrations are definatley more noticable when NOT accelerating, but also NOT hard braking (decelarations). It seems to be more prevelent when slowing down or moderate cruising speed. Like when letting of the gas slightly or lightly braking, but not a warped rotor vibration. This 2014 has only 4k miles. A few Jeep guys, that are wrenchers, said its sounds like the backside of the diff pinion gear, or ring gear. There is definately an issue, thankfully I don't drive it must or very far, daily My service manager has mentioned the rear diff, but doesn't have a definate answer or confimation. keep y'all posted

@ kchaggins - That is the most ridiculous comment I have ever read, If it's not your concern, why bother write 5 paragraphs. I paid (or am paying) for a $44,000, "Professional Grade" truck, I don't expect it to drive like BMW or handle corners like a Corvette, but it should not be vibrating. As for the "mpg" , most truck owners don't buy the vehicle for gas mileage efficiencies. That is a government mandated number that the manufactures must meet. Thankfully this model can be switched to V8 mode, minus 6th gear, by method described by 'EastCoast HD' in previous post. Thank you 'EastCoast HD' for confirming this feature, I thought that there was something wrong with the "manual mode' , as I was trying different gears to check for the vibration issues. On a seperate note, I also noticed the "traction control" doesn't actual shut off. Or it does, but the " stability Track" stays engaged to prevent the rear end from breaking loose above ~ 30mph or from coming around, preventing the "power slide" or "donut" horse play. Again a mandated "safety" feature. Anyway, My 1993 Ford Ranger V6 Ext Cab w/ 4" suspension lift and 33" BF Goodrich never vibrated. I was original owner and installed al the goodies after warranty expired, never had a problem. Goes to show, more technology, more bells and whistles,....more potential problems. This vibration was noticable when I test drove the truck, but was told it was a"flat spot" on tires from sitting as it was an early model. I called bullshit, and the sales guy said it's all under warranty if there are and issues.. Now they just need to find the cure for the issues. BTW..I wont let it bother me anymore if 'kchaggins' wants to make my payments, lol....actually it would still bother me, just slightly less

UPDATE: 2015 Sierra Z71 DBLE Cab, SLE 5.3L 4x4 , Still Shaking after 3rd trip to GM dealer. This time they tried the replacing the rear shock as per a Tech Bulletin to cure the 70mph shake. Haven't driven the highway enough to determine if that vibration is fixed. Predominately the vibration is from 30-45mph at low RPMs in High gear, either 4cyl or V-8. Might buy the Range Active Fuel management module to keep it in V8 mode, but don't want to spend $200, when I personnally think it's a driveline , Transmission , or axle issue. Anyone try that module??? I feal bad for the dealership cause they shouldn't be the R&D depatment of GM. I will be issuing a "Non-comformance" to GM and will be requesting a "Corrective Action" to their Quality Department. After all I believe they are ISO9001 compliant.

Well my truck is at the dealer in Arlington , TX for the 3rd time. It's the same runaround I wold expect from a company with no spine. "Nothing out of the ordinary" doesn't not mean it's right. just means the rest ov the vehicles are just as bad. I think they are as frustrated aa I am GM for not having answers of avoiding the situation. They loaned me a 2016 Sierra Crew cab, and it doesn't shake, but ever so slightly. Much less than my truck. But it's not a Z71, not a Dble Cab, has diff wheels and tires, not sure what rear diff .....so it's an apples and oranges comparision. They may be letting me drive it with the PICOmeter installed to get some data....As an engineer, I'm not opposed to it, but I'm not doing their jobs........we shall see

So I have seemed to found my support group for distraught GM pickup owners that are experiencing vibration issues with their vehicles. I have been dealing with a similiar issue with my 2015 GMC Sierra SLE Z71 4x4, Double Cab 5.3L with 4500 miles. I purchased the truck NEW in January as an "early 2015" promotion rebate, in NY and drove it to Texas where I have relocated. When I bought the truck, there was a vibration that the dealer claimed was a "flat spot" on the tires from sitting on the lot for months (since August). I figured it was plausable, or just stiffness of components that would loosen up over time. Well it's been almost 6 months and 4500 miles later and I have noticed an abundance of other intermttent noises and vibrations. All of which are unacceptable of a NEW "Professional Grade" $40K+ truck. After about 1000 miles I would occassionally hear and feel a clunk from under the vehicle while driving at 45mph as the vehicle shifted into 6th gear at around 1200 RPMs Then I began to notice a chattering vibration at about the same MPH and RPM on the same section of road in a village speed zone. This all occured in NY in very cold temps, near 20 degrees. This vibration was akin to letting out a manual clutch in too high of a gear. If I selected "tow mode" it appeared to happen less often. Now for the more annoying and reoccurring issue.... The vibration or oscillation that occurs at 30-40mph. This also occures periodically at 65-75 mph when cruising on a highway. There seems to also be a harmonic vibrationwhen hitting small "high speed" bumps at those speeds. As an Electrical Engineer, I have experience in vibration testing and as a retired amateur superbike racer I am extremely accute to suspension dynamics. I can not pin point this to a suspension component, but I can definitley say it is not a tire tread issue or a balance issue as the dealer claimed on my first visit,I believe it to be a drive train issue, either the Transmission, drive shafts, or Differential. After my second trip to the shop they indexed the propshaft and reset the body to the frame. Neither fixed the problem. I wish I could say it's hard for me to believe GM would put such poor quality out to it's dealers. But considering the shady buisness of the bailout, they don't care about the little guy. I traded in my 2007 Siverado extended cab Z71 for this headache. Previous to that I had a 2004 Silverado extended cab Z71, Both were V8 5.3L 4x4 standard box. Neither of which vibrated Seems GM's answer is to send out Picometers, measure the vibrations, and set the acceptable allowed vibration at a level to exclude most the vehicles that at a nuisance. In my line of work this is called "Derating your Spec" and it's a poor practice for poor quality Is anyone starting a class action law suit? Seems there are enough cases