Bought a 2014 ext bed GMC Sierra 1500 in Sept 2014, brand new. It has a 6 cyl in it, not a V8 which is unusual. I did not mind, as I had (have) no plans to haul anything with it. Around 113,000 mile, in early 2022 it started "bucking, jerking" at high (5500) RPM as the transmission moved (moves) from 2nd to 3rd, 3rd to 4th. Changed spark plugs, changed plug wires, changed A.C. belt, changed serpentine belt, cleaned fuel injectors... and now I am getting a new CAT converter put in... and nothing has changed, still all the same issues.

Should get it back today with the new CAT... we will see, but so far, have spent $5000 with absolutely none of the problems fixed (local authorized GMC service center Grand Jct CO). Hopefully the new CAT fixes the issue. Very disappointing for a vehicle I take such great care of and bought brand new. I really think the local GMC service center is doing all they can, I think it was (is) a factory design, manufacture problem. Searching around online, with all the complaints specific to 2014-15 GMC sierra and Chevy Silverado vehicles, the blame seems to point toward design, manufacturing.