I purchased this vehicle on Oct.16/14 from Pye Chevrolet in Truro ,N.S.,Canada.Dribving it home there was a Vibration at different speeds.Called the sales person about it thinking it was probably a tire out of balance.She advised to take it to the local GM dealer to have it fixed.And so began a three year circus.The dealers(as the local dealer is not where the vehicle was purchased)have tried every conceiveable way to dodge the underlying problem which after the second year I learned from a GM mechanic is caused by the V4 mode in the engine.This was proven by the mechanic when he had his computer hooked up to the vehicle during a test drive.However the service manager would not provide a copy of the test results.They have balanced tires,rims,tire and rim assemblies on and off the vehicle,replaced the drive shaft,reseated the cab to frame,tinkered with the computer in the vehicle,adjusted the exhaust,installed a section of adjustable exhaust,adjusted the motor mounts and clamped a piece of lead to the exhaust all in the hopes of deadening the vibration to the point where it is not felt in the cab.But they refuse to attempt to fix the problem in the engine and under direction from GM they refuse to admit the vibration in V4 mode exists.The vibration happens when the V4 to V6 is about to shift.Problem is the RPMs are too low before the shift causing the engine to flood thus causing excess carbon being produced which is going to cost the consumer money down the rd in fouled plugs,O2 sensors,valves and who knows what else.I reported the excess carbon in the exhaust to the dealer and he said that was normal,so normal that the whole side blew out of the muffler in the second year.The last time I had into the dealer was Oct.2017,the month that my warrantee expired and they report that they tested it with a pico scope and said it was a 1ST ORDER TIRE VIBRATION.We are right back where I was 3 years ago so until everyone with this problem,and there are thousands plus,unite under a class action law suit and force GM's hand this will continue whilethey sell these faulty engines day after day.Time to look for another brand.

vehicle vibrates at various speeds from slow to highway

New truck developed vibrations at speeds from 23 mph to 70. Thought it was unbalanced tires but after dealer

balanced all 4 wheels problem persisted and got worse over time. Returned to dealer 3 times. First two visits they performed some type of instrument tests, telling me it was the engine's changing from 6 cylinder running to 4 cylinder (as it is designed to do). Vibrations got worse during greater variety of speeds. At third visit dealer refused to perform another test; instead tech drove it for 10 miles at various speeds (so they told me) and announced that vibrations were still "within normal factory limits":. Dealer refused to perform the instrument test because"tech would not get paid for it, GM would not pay for it; dealer would not cover cost and the dealer knew I would not pay for the cost of the test". So much for help from the dealer. Problem continues to get worse.