2015 Silverado C.C. 4WD - NEVER had an ounce of vibration in 25,500 miles...I work away, so I run the Pa. turnpike twice a week. or so...about 110 miles each way @ 70+ mph...
UNTIL...
I dropped the truck off 2 weeks ago at the local dealer here in ohio to get the 3 recalls done, seat flex fixed, and I let them do the free oil change/rotate tire service, which I never use, because its inconvenient for me.
recalls were airbag, seat belt, and 4wd issues...
after picking the truck up, I drove it locally, to work, and then to home and back on turnpike...about 300 miles with no issues...
Tuesday before Thanksgiving, I had to take care of something 20 miles away, so I got on the turnpike after work, and getting up to around 74 mph, the steering wheel was shaking, and the truck vibrated like never before...I slowed to 65...no change...to 55...still vibrating...
I would have bet money that a wheel was coming loose...but after pulling over and checking all with a wheel wrench, all are tight...
vibrated the rest of the way...took care of business...then checked engine/trans oils...crawled underneath...nothing seemed out of place or loose.
next, while going up a slight grade, I noticed when the trans shifted into 3rd or 4th. the engine revved a couple hundred rpm...like it slipped...it did it once more after I had to slow for traffic.
on my way back to the highway, I put it in and out of 4 w.d. a few times...
got on the highway, and the vibration was gone...next day, going home on the turnpike, no vibration...on the weekend I even had it up to 85 on I-70...no vibration...back to work Monday morning on the turnpike...no vibration...