Issues with emissions switch. Check engine light will not go off. Also 3 and 4th gear are completely gone out. I do not tow or have had anything even remotely heavy in this truck. It's a 2005 GMC Sierra with only 78,480 miles on it. I am not the only one having issues with this 4 speed transmission. It is not heavy duty enough for this size truck. GM needs to recall all of these transmissions. When it first started slipping I lost all power going down the road at about 55mph. The vehicle that was behind me slammed on his brakes to avoid hitting me. This problem with the transmission is going to kill someone.

- Wayland, NY, USA

Within 4 months of purchase, was driving at approx. 25 mph when transfer case shifted into 4 high on it's own. Shut off vehicle, restart and able to put back into 2 wheel drive. Happened on and off for a little more than a month when it went to 4 lo while driving at 30 mph through town. Unable to reset. Limped it the 2 miles to dealership for diagnosis. Cost me $1200 to have the transfer case rebuilt. Smoked the clutch pack, burned out 2 bushings and bent shift shaft. Had second issue of shifting on it's own, May 15th, 2014. This time it cost me $500 for the shift motor to be replaced. Second problem, speedometer reading incorrectly or not at all. Been going on for about 3 years sporadically (apparently the little drive "motor" on the back of the instrument cluster, $300 replacement or, found a company to rebuild with new "motors" for under $200). Passlock issues started in Jan 2014, has left me stranded a couple times now. Can't get a good answer from dealer as to how to repair other than "bring it in and we'll hook it to our diagnostic system" (I.e. pay us lots of money). Also having issue with check engine light on constantly. Intermittent engine miss on multiple cylinders. Rough idle, crappy mileage, but not down on power. Miss seams to go away off idle and not noticeable under load. New plugs, wires, etc, etc, etc.... haven't figured this one out yet. Same answer from dealer (pay us more money please). Lastly, air bag light came on in Dec of 2012. Never crashed or bumped but had to replace left front air bag sensor. Love the truck, currently has 154000 miles but I'm getting frustrated with all the little electrical "glitches" and the dealer won't help a bit without the normal answer, "bring it in and we'll hook it to our diagnostic system". it's dang near $200 (diagnostic charge) just to get my truck in and out without even getting anything repaired!

- Junction City, KS, USA

2005 GMC Sierra slt VIN [xxx] I drove the truck 237 miles home and noticed it was not operating properly. I called GMC to resolve the problems. The truck has binding in the front axles, brakes, or differential. This causes the truck to understeer heavily as the truck works to turn the front wheels over the road surface. This also makes the truck difficult to steer, U turns are especially a problem, the truck has sluggish acceleration and stays longer in the lower gears. The rear tires are prone to lose traction due to the increased rolling resistance from the front wheels, braking performance is compromised, the truck will sway back and forth at highway speeds as the rolling resistance of the front wheels varies from side to side. The truck tends to pull to the left, and the suspension is always preloaded from the additional stress. The engine labors to maintain speed on level ground with the vehicle unloaded. On occasion the front wheels will hop off the pavement as it is easier for them to compress the suspension/torsion bars than be turned over the road. It is difficult to maintain a straight line with the truck since the front wheels tend to follow the Contour of the road. The front wheel assemblies make a low frequency sound when driving. The transmission, engine, and drivetrain components are always loaded and driving on snow or ice would be treacherous since the front wheels would stop turning on the low friction surface. Driving in the rain is bad enough and the rear wheels tend to break loose. The transmission has behaved strangely, stuttering on occasion as it tried to find the proper gear, it has slipped or freewheeled as I went to accelerate from a stop. The wrong oil filter was installed, the air cleaner is loose and rattles in the engine compartment. The power steering provides little or no assist and requires more effort than I have ever experienced from a vehicle that is supposed to have power steering. Updated 07/17/2012 information redacted pursuant to the freedom

- Tucson, AZ, USA

I own a 2003 2500 hd 4X4, a wonderful vehicle it would be even more wonderful if I could find a dealer that would stand behind his product. My next car probably will not be GMC or Chevy. I have owned the car since June of 2003. Due to the nature of my business I already have 98,000 miles. During that time I have complained about fuel mileage. The reports lie. Nobody will do anything about the fuel mileage. Because it can't get any better because they lied. I have lost a vaccume pump, and a left front wheel hub which had to be completely replaced. What prompted my complaint is that I have started developing a vibration at 77-83 mph. Dealer rep says you shouldn't be doing 80 mph. Therefore since our mechanics can't speed in your vehicle ( completely understandable) you don't have a vibration. Despite the fact that the vibration occours at 80mph I still have a vibration and just because it is against the law, ( 75 is about the norm on our highways), doesn't mean I don't have a vibration. My guess is that it is either another wheel hub, or something in the installation of the new vaccume pump. Because after they replaced that it ran good for awhile. The vibration is getting worse and I am at 97-98,000 miles. Vehicle is also starting to surge, but not all the time. From what I have read about the other complaints it could be the ac acting up. But since it wasn't surging this time, well if your a consumer reading this you know the story. I have told you all the bad. Now for some good.... the brake system on this car is beautiful I am still less than half all the way around. The brake system is perfectly tuned from front to back. I have hauled cars and trailors from time to time and the engine transmission and brakes all work together beautifully. Its the service I am complaining about.

- Corning, CA, USA