Transmission does not downshift when RPM's fall to 1000 due to slowing traffic, turning, etc. When trying to accelerate normally vehicle lugs and hesitates and will not accelerate. If throttle is significantly increased the transmission downshifts several gears and accelerates rapidly. The higher the load on the vehicle (ie. A/C or going uphill) and the higher the ambient temperature the worse the problem gets. When cruise control in engaged the vehicle will slow down as much as 4 mph before downshifting to maintain set speed. This is a safety hazard due to lack of acceleration when required and also sudden rapid acceleration when vehicle finally does downshift. General Motors engineering states that this is due to design to increase fuel mileage and refuses to address the problem. This problem has been present since I purchased the vehicle new in April of 2015.

- New Carlisle, IN, USA

Similar to other complaints, the vehicle nearly stalls when taking off from a stop. The transmission is in the wrong gear and the acceleration is very limited unless the gas pedal is pushed down fully. This causes a very dangerous situation particularly when turning left at intersections as the vehicle will nearly stall or move at a very slow pace. This has been happening since day 1.

- Mansfield, TX, USA

When stopped or maintaining a low speed (e.g. in traffic) when the accelerator is slightly pressed the truck will hesitate and have a slight jerking motion. Will need to almost full press the accelerator to get the truck moving. Brought the truck to the dealer on 3 separate occasions just for them to say that there is nothing wrong and that hesitation & jerking is 'normal'. the 'normal' diagnosis drove me to do some research on this issue and come to find out that other people with the same make, model, year are having the same issues. I have noticed this issue since I had purchased the vehicle back in August 2015.

- Bridgeport, CT, USA

Hesitation when acelarating bad almost got in wreck took to Chevy dealer they know about it would not do anything about it only has 9050 miles on it. In motion.

- Niles, MI, USA

Truck transmission does not down shift when slowing down at times or when taking off from a stop light. Returned to dealer twice and second time they did a software update but still doing same problem. Dealer say's truck normal. Waiting for an accident because transmission will not shift correctly also not shifting correctly at times when passing other vehicles.

- Hernando, FL, USA

The contact owns a 2015 Chevrolet Colorado. After the vehicle was started, it hesitated to accelerate form a stop. The failure recurred three times. The vehicle was taken to a local dealer where the technician stated that the transmission needed to be serviced. The vehicle was repaired. After the repair, the vehicle experienced occasional stalling. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure. The failure mileage was 18,000....updated 09/14/16

- San Francisco, CA, USA

The contact owns a 2015 Chevrolet Colorado. While driving various speeds, the accelerator pedal was depressed but the vehicle hesitated before accelerating. The failure recurred on numerous occasions. The vehicle was taken to a dealer where it was diagnosed that the vehicle functioned as intended. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 6,000.

- Carlsbad, NM, USA

Vehicle bucks and hesitates when pressing gas pedal riding in 6th gear at speeds up to 50mph. If you give it gas it gets worse and finally after 5 secs it will down shift 2 or 3 gears and go way to fast. I have taken it to dealer twice and they said transmition was still in learning mode and should clear up. Well its at 15,000 miles and still has problem. If I put it tow mode it does not happen...shift point calibration is needed badly on this truck

- Hartly, DE, USA

Truck has 11K miles. When breaking at low speeds, I get a lot of break squeal. This happens driving forward or in reverse. Also, when driving the truck has a hard time shifting and makes a rattling/pinging noise when it is trying to find the correct gear. This happens sporadically when driving slow, fast, uphill, and mostly occurs during acceleration. The shifting issue happens on the freeway as well as city streets.

- Danville, CA, USA

Similar to other complaints, the vehicle nearly stalls when taking off from a stop. The transmission is in the wrong gear and the acceleration is very limited unless the gas pedal is pushed down fully. This causes a very dangerous situation particularly when turning left at intersections as the vehicle will nearly stall or move at a very slow pace.

- Gibsonville, NC, USA

The contact owns a 2015 Chevrolet Colorado. While driving 20 mph and downshifting in manual mode, the vehicle lunged forward. The vehicle was taken to the dealer to be diagnosed. The contact was informed that the vehicle was functioning as designed. The contact also stated that the access door sensors failed. The vehicle was not repaired. The manufacturer was notified of the failures. The approximate failure mileage was 90.

- Fayetteville, PA, USA

When driving at low speeds, it feels like the transmission is in the wrong gear, because when you need a fast acceleration, the car bucks and almost feels like it's going to stall. It seems like it is searching for the right gear and therefore it takes time to react. I have been on a few close calls, almost got into an accident a couple of times because of this bucking and delay on reacting when you need to get the power from the engine.

- Spring, TX, USA

Like many of the other complaints listed for this vehicle. This problem routinely and repeatedly occurs on both street and highway driving. After slowing down and depressing the accelerator, the automatic transmission will stumble and hesitate. Because the vehicle won't readily accelerate, the gas peddle is depressed further and then the automatic transmission will downshift too many gears and excessive acceleration and engine RPM follows. This problem causes excessive acceleration, which could place the vehicle and its occupants into an unsafe traffic situation and potentially cause accident and/or injury. The dealer service writer was asked about this situation and responded that "the transmission was seeking the best gear to maximize gasoline mileage performance", which really doesn't seem to make sense in this situation.

- Los Angeles, CA, USA

When starting up a hill, at a slow speed, the transmission, will hesitate, almost stop, until the gas pedal is pushed down to get the vehicle moving. This is an ongoing problem, I have been told by dealer, that the transmission is adapting to my driving style, and will soon improve.

- Roanoke, VA, USA

The transmission won't downshift while trying to accelerate after slowing down. The truck will start to very noticeably chug and jerk and not want to go from not downshifting when braking and then trying to accelerate. I have been close to getting rear ended when this happens and to avoid it I have to stomp on the gas pedal which then causes it to jerk erratically from downshifting too far and causing me to accelerate too fast and almost rear ending the vehicle in front of me. This happens every time I slow down to go around someone turning or slowing down to stopped traffic and then accelerating again. While driving with my wife at around the 200 mile mark it started chugging badly and she thought we were breaking down. It is very embarrassing when someone is riding with me because no vehicle should act like this. GM should be ashamed of themselves. I have about 10,500 miles on my truck right now and this issue has been a serious issue since I drove it off the lot brand new. Took it to the dealer and they said it should take a couple seconds to shift from gear to gear. Its funny because I have driven a lot of vehicles and none of them have done that or took that long to shift. I know the transmission is supposed to adapt to your driving...which seems very unnecessary to me but obviously it is not working out for the Colorados. Adaptive transmissions need to go and put a firm sporty shifting transmission in these trucks.

- Canton, NY, USA

Purchased truck in November 2014. Crew cab Z71. Had problems right at 200 miles. They said the transmission has to learn my style of driving. At 2,00 miles transmission and engine still don't talk to each other. I can accelerate and 5 seconds or more later the transmission reacts. In heavy traffic, a couple of cars get between me and the car I was following before it reacts and I have to slam the break. Always seems to be in the wrong gear. Will chug a lot until it gets up to the speed for that gear. Took it to dealer at oil change and they reset the control module. After 2,000 more miles, took it back because it still acted the same way. Took tech on drive and was able to duplicate all my concerns. He said that there was nothing he can do and that I needed to wait for ECM calibration from GM. He said he felt bad for me. Surely I will get in an accident because of this slow transmission that is always in the wrong gear. Currently I am at 7,000 miles. The only thing the tech could say was not to drive it in stop and go traffic....seriously. Clearly this adaptive transmission is bull crap and GM probably knows they have a piece of crap programming but can't figure it out. Please figure out this shifting problem, because other than this the truck is nice...too bad, because if they don't someone will get in an accident and hopefully it will not be fatal. Get rear ended because it doesn't accelerate when you need it to, or it finally moves when you are needing to break. Fix this now or at some point you will pay big....

- Rochester, NY, USA

Purchased 2015 Colorado in August. While driving it I have noticed there is a problem with the transmission and engine synchronization between down shifting and maintaining proper RPM's. when driving a steady speed in traffic and you need to speed up a little the transmission does not down shift. When you give it gas to speed up the engine the rpms are to low and the engine bucks and is lugging very badly. You are at a point it feels like it will stall. This lugging has to be bad for engine. If you press down harder on the accelerator the transmission will down shift suddenly and the truck will surge forward quickly. I have almost run into the rear of vehicles while in traffic and trying to maintain flow speed.

- Orrtanna, PA, USA

I wanted to reach out to you on Chevrolet"S claim that their engine achieves 305 horsepower. While it may be true that their engine achieves this figure it does so at a stated 6800 RPM. The 6800 figure is important to note because the trucks? red line indicating potential dangerous operating conditions start at 6500 RPM. So in essence in order for an owner to achieve 305 hp they would have to be operating their truck in a potentially dangerous manner. Even in the 2015 Colorado owner?S manual it indicates the danger of operating above the redline? ?do not operate the engine with the RPM?S in the warning area.? GM is stating that someone can achieve maximum hp only by operating the vehicle in a dangerous manner....really"! I believe it will only be fair for Chevrolet to re-evaluate their maximum horsepower prior to their engine hitting the redline.

- Costa Mesa, CA, USA