2,400 miles and this vehicle has been back to the dealer four times for "chugging and shuttering" in heavy traffic. Driving though an intersection with heavy traffic it will not keep up with traffic but tends to bog down almost getting rear ended from behind. If you try to smoothly accelerate it will rapidly downshift and jump forward almost rear ending any vehicle in front. Very unsafe to drive. Trying to drive with the flow of traffic at 35-40 mph the truck shutters as if the spark plugs are worn out. Also trying to accelerate into on coming traffic it will sometimes chug to where you wonder if it's going make make the merge. Very frustrating to drive for a brand new truck, the dealer replaced the torque converter at 500 miles, then has preformed service bulletin #pip5342B three times with absolutely no improvement. GM states in the bulletin "note: Preforming this calibration update may not totally address the shudder or chugging concerns" how can new vehicles continue to be sold with this known problem? not only is it frustrating trying to drive smoothly, but it is also a safety concern. Due to the poor performance the mileage is about 13 mpg in city traffic, not even close to the mileage rating of 17 mpg.

- Cape Coral, FL, USA

While driving the 2016 Colorado, the transmission/engine seems to have trouble shifting and accelerating and the shift patterns are erratic it seems, maybe its the fuel efficient crap that shuts down cylinders, maybe its the trans?. experienced it on highways and lower speeds, stop and go traffic, truck's transmission clunks, shifts hard at random and stutters allot. It's aggrivating. When trying to pass, seems to be zero acceleration felt when flooring it then suddenly kicks in (roughly)..like oh hey-I need to go.. I could get in a wreck-ended because of this and I better not try to pass anyone.. I feel my safety could be at risk with as much hesitation then suddenly lurches as it has. I see quite a few complaints already concerning this and/or describing just about the same ordeal. Daily - but random - city and highway, turning, straight etc. Basically any situation but idle.

- Dayton, OH, USA

--- "the transmission does not downshift from a high gear (5 or 6) to a lower gear when slowing down from 45 mph to 20 mph (or lower). When the accelerator is depressed to accelerate the engine bucks, vibrates, and does not accelerate. The engine RPM drops to 1,000 RPM or lower. If the accelerator is quickly floored the transmission downshifts several gears lower and jerks forward. This condition happens primarily on secondary roads while driving along the road and when pulling from one road into traffic on another road. The situation when pulling into traffic is dangerous because the truck does not accelerate as it should. This truck was purchased new and has 1,500 miles on it. This condition has been present since the truck was new and the severity varies with truck speed and road inclination. The situation has been reported to the dealer and to Chevrolet customer service. No corrective actions have yet to be made."

- Pittsfiled, MA, USA

When merging onto I-70 freeway from on-ramp, I applied throttle to move into the traffic flow. Engine "stumbled" as if in a dead spot. Truck did not accelerate and appeared to be lugging badly. Transmission was in too high a gear and seemed to be searching for correct gear. During this time oncoming traffic was forced to brake and there was a near miss of having a rear-end collision. All I could do was watch in the rear view mirror as traffic converged on me. This "dead throttle / wrong gear" issue has happened repeatedly on surface streets but luckily on surface streets I was not in such a critical situation. This is a problem that has been reported repeatedly and at many places on the internet. When will NHTSA force GM to address this issue? hopefully you will act before this results in serious injury or fatalities (if it already has not). Please act!

- Golden, CO, USA

Engine seems to lag under quick acceleration. Problem occurs most often when accelerating from a turn or when changing lanes under acceleration. Speeds of occurrence mostly approximately 20-25 mph. Requested checks and service at a dealership only to be given a service bulletin from GM stating this was a normal part of the traction management system. My previous vehicle (2014 Silverado) was also listed on the bulletin, but the problem was never noticed on this vehicle. I see this issue as an increased risk of a collision with the highest risk being a rear end collision. This needs to be addressed and fixed.

- Albuquerque, NM, USA

Driving at about 60 miles a hour and lost all power engine was running but going no were all light were lite on dash like you turn key on before starting thank god no one was coming the other way or the car behind me would have hit me. He was a good driver. Shut it off and restarted it then it would run with all light on dash even brake light and anti skid light and it said on infro. Running at reduced speed. Drove to my home a slow speed it let me. Shut it down let it sit a few min. Restarted it still the same. Shut it down for about ten mim. Restarted it. Seem to run ok but check engine light is till on now I afraid the will just reset it and say it is ok. And next time I won't be so lucky. It has 5500 miles on it. I did see my life before my eyes hopping it dose not happen to others. Taking dealer tomorrow it happen at about 5pm 3/24/2016

- Harrisburg, PA, USA