While driving car bucked and shifted irregularly, transmission slipped, no power, no reverse.

- Aquebogue, NY, USA

Warning indicators turn on for the system braking components such as ABS brake failure, traction control and loss of engine power while accelerating between 35 to 50 miles per hour. Engine power decrease and the car speed and power is decreased with the loss of engine power warning. The car would just stop at this point. I contacted onstar each time this issue occurred to a diagnostic scan and each report indicated that same warning reported on the console. After 10 minutes the vehicle would re-start and I was able to drive it. This issue has re-occurred within 2 years and the GMC service department was unable to diagnose the problem but during the latest incident the mechanic had ruled the issue as low brake fluid. I've investigated this issue online on various blog forums for the GMC Acadia with the same description of braking system failure and others report the failure as an internal braking malfunction in which the master cylinder leaks into the brake booster. I'm concerned that this problem could potential become fatal is it recurs. The GMC service department refuse to look into my concern and investigate the problem. There are no visible signs of a leak because the leak is internal.

- Pflugerville , TX, USA

Vehicle has a delayed shift into 3rd and 5th gear, with a vibration felt in those gears. Found codes P0717 P0716 for input speed sensor on transmission. It is believed the vehicle has a broken 35R wave plate and need to tare down to inspect or replace transmission at only 63,000 miles. Extremely common problem on these vehicles (please refer to GMC Acadia forums online everywhere for other victims).

- Hermiston, OR, USA

Vehicle experiencing bad transmission problems when shifting between 3rd and 5th gears. As accelerating, the vehicle begins to shift, but begins to idle and RPM's rise extremely high. Vehicle begins to slow down and finally jerks into the next gear causing rapid acceleration. This issue almost caused me to run into a car in front of me after pulling off from a stoplight. It is extremely scary to continue to drive the car, but with this being my only vehicle and I must work, I am forced to drive daily. Warranty just expired 5 months ago in March and I cannot afford to fix the problem (March 24, 2013, 5 year/100,000 mi. Powertrain). Vehicle was purchased March 24, 2008.

- Upper Marlboro, MD, USA

I was at my son's baseball game and went to move my vehicle when I was pulling out of the parking lot and the vehicle started revving and would not move other than coasting (since I was on a hill). I was 3 hours from home and had to have the vehicle towed to the tune of $300 +. I have since had to have the transmission replaced. This has cost over $4500 not to mention having to drive 2 vehicles with my family since the Acadia was the larger of our vehicles.

- Sayre, PA, USA

About a week ago my family and I were driving home from vacation and had been on the road for about 3.5 hours. As we pulled out of a driveway about 5 minutes from our home the car engine light came one, the car would not gain speed like normal and it began to over heat rapidly. We took side roads and slowly crawled home. I took it into the shop the next day and it came back with a crack in the radiator and codes P0700 and P07016, which they confirmed to be a transmission issue and suggested to have a specialist look at it. I did some research and found that this are common codes that come back for the 2007 and 2008 Acadia's that require a rebuild/replaced transmission with an average cost of $4000. This is a known issue with GMC for many years and they have yet to acknowledge it. I am very lucky to not have had a worse incident in discovering this issue, but I am very concerned that at any moment the transmission will go out, and we do not have $4000 to drop into a new one, especially when I just spent $650 on a new radiator. These are not problems that a reliable car, the 2008 Acadia, under 100,000 miles should be having. GMC needs to own up to these issues and take action to correct it before something more serious happens.

- Rocklin, CA, USA

While in traffic, my engine revved up and my vehicle jolted forward when my transmission stopped working. If anyone would have been behind me, there would have been a major accident.

- Pearland, TX, USA

While driving on a highway, the car went into neutral and lost power. After a few seconds, it went into low gear and would not shift into a higher gear. The transmission required a re-build two years earlier at 62,000 miles and is now failing again. We were told the transmission must be re-built yet again. We cannot drive the car as the loss of power and slipping transmission is very dangerous. The transmission design, and the subsequent repair by the dealer, was faulty. As our warranty expired 4 months ago, we were a new transmission was required at $4,000.

- Eastchester, NY, USA

While driving down interstate state at 70mph I came up on slower traffic and had to slow down to 60-65mph before I could change lanes. Once changing lanes and as I went to accelerate the vehicle seemed to downshift and RPM went from 1800-2000 to 5000 and the vehicle basically stalled for about 5 seconds causing a 18 wheeler to basically all but wreck to keep from killing me and my other 5 family members in the vehicle. I pulled over at the next exit and made sure there was no kind of transmission codes or anything to show up on the dash but I still checked my fluids and everything checked to ok. I had 325 more miles to get home so I basically had to baby it to the house. It happened several more times during the trip but that was the worst. I have also experience on several occasions that the airbag in the passenger side front seat turns itself on and off for no apparent reason with the same individual sitting in it who weighs 130lbs. At first I just thought it may have been the way they were sitting but I weigh 200lbs and it did the same with me. I'm hoping to get these problems resolved by dealer tomorrow but with so many transmissions doing the same thing the gov & GMC need to take charge of this issue and get the [xxx] problem fixed before more people have issue and get killed or injured. Information redacted pursuant to the Freedom Of Information Act (FOIA), 5 U.S.C. 552(B)(6).

- Columbus , MS, USA

On the first occurrence I was starting to accelerate to about 20 mph after being stopped at a red light and my power steering went out and I could not accelerate. I was barely able to steer my car off the highway and just missed hitting a tree and going in a ditch and my 2 children were in the back seat. I had the vehicle towed to the local dealership but there were no error codes showing on their computer. I have since had this happen 4 more times and the last time almost ended in a head-on collision with my children in the car. I had the car towed again for the 5th time to the dealership and the power steering finally went out on them while they were test driving my car. However, the computer still did not show any error codes after this happened. As of today, which is 3 weeks later, I still do not have my car and the dealership doesn't know what to do because there are no error codes eventhough the power steering keeps failing on them. I am frustrated and aggravated and after reading online at how many other drivers have experienced this exact same issue I am disgusted that GM has done absolutely nothing to fix this serious issue.

- Daphne, AL, USA

My friends and I left a store and was pulling out onto a busy route. Speed limit is posted as 45 mph. I was idling at the stop sign waiting for a vehicle to pass. When it did I pulled out into traffic. I gently pressed on the accelerator and that is when I felt the truck jerk and then the pedal was floored!!! I was not doing this!!!! I was in amongst the traffic, trying to Dodge others, and then I tried to turn my truck off. I couldn't do it. It was not allowing me to and the speed had increased dramatically!!! I reached down and was messing with the accelerator hoping to pull it up from the floor. The accelerator was completely pressed into the floor as if someone glued it there. I crossed over 3 lanes of traffic trying to Dodge vehicles and trying to prevent a crash. I finally managed to free the accelerator. It freaks me out when I drive now, .

- Farmer City, IL, USA

The contact owns a 2008 GMC Acadia. The contact stated that she utilized the cruise control at 50 mph. The following day, the vehicle abnormally accelerated from 40 mph to 50 mph without warning. The cruise control function was not being utilized at the time of the failure. The vehicle was taken to the dealer for diagnosis and a test drive, but the failure could not be duplicated. The cause of the failure was unknown and the vehicle was not repaired. The manufacturer was not notified of the issue. The failure mileage was 60,000. The VIN was unavailable.

- Muscatine, IA, USA

I noticed that when driving on an expressway and would attempt to pass a slower moving vehicle, as I would move into the passing lane and attempt to accelerate, the car would hesitate for a few seconds, lose speed, then suddenly downshift and accelerate at an unexpected rate. I also noticed that the car would unexpectedly accelerate or decelerate under normal driving conditions. I bought the vehicle to the dealer for repair, they responded that they could find nothing wrong, but the what I was experiencing was characteristic of the 6-speed transmission on the vehicle. The problem continued and I found it dangerous. I returned the vehicle and the dealer's remedy was to "reset the transmission computer." During this time, I also noticed that the "service stabilitrac and traction control" warning would come on. Onstar recommended I shut off the engine to reset the system. I found this only happened when I first used the car in the mornings to go to work. Again, the dealer said there was nothing wrong and the computers were showing no codes -- they also stated that they could not duplicate the problem. I got the car back from the dealer and it happened again - at 7:00 am. I called onstar and they gave me two codes. I bought the car back to the dealer and gave him the codes. It now seems that there were two defective sensors controlling the stabilitrac / traction control system and how they communicate with the transmission. I was told that GM is changing manufacturers on the sensors. I have not had use of the car since the beginning of June and am still waiting for GM to produce these parts. In the meantime, unexpected acceleration, deceleration, and gear shifting was occurring under all driving situations causing -- in my mind -- a danger to myself, my passengers, and others. The dealer has had the car on five different occasions since June 8. this last service they have had the car since July 20.

- Brooklyn, NY, USA

Power and power steering failure- when it rains or I drive through puddles of water the car looses power and slows. Also when I am driving the power steering stops working and there is a loud squealing noise. I had the dealer look at my Acadia and they said they could readjust the belt guard. This did not work and they said just be cautious while driving. Also the cruise control doesn't coast and the speed increases as you go down hill.

- Republic, MO, USA

We purchased a new GMC Acadia on 6/16/08. Since our purchase, we have experienced a dangerous transmission issue. After coasting downhill, the vehicle fails to downshift which causes a rapid deceleration when traveling uphill. This rapid loss of speed puts the driver in the hazardous situation of a rear end/chain reaction collision on the road GMC claims to have a fix, but this fix causes the documented gas mileage to be reduced by at least 2-3 miles per gallon. They have attempted to fix this issue twice in the last 4 weeks to no avail.

- Pittsburgh, PA, USA