Overview & Reviews

The Sierra gets a revised look this year that includes a new front fascia, revised side moldings and optional multifunction, fold-away mirrors. On the inside, GMC has added new seats, a more comprehensive driver information center, a redesigned instrument panel and optional dual-zone climate control and satellite steering wheel controls. On the hardware side, the standard 6.0-liter V8 gets electronic throttle control as well as the ability to run exclusively on Compressed Natural Gas (CNG) or a mix of CNG and gasoline. Other upgrades include an improved Insta-Trac part-time four-wheel drive system for reduced service costs, a more efficient starter for the 8.1-liter V8 and a revised headlight switch that allows drivers to turn off the daytime running lamps.

• Powerful drivetrains, roomy interior, numerous available amenities.

• Spotty build quality, cheap interior materials.

User Reviews:

Showing 11 through 20 of 26.00

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  Cant wipe the grin away - 2003 GMC Sierra 2500HD
  By D/A Guy - March 11 - 10:00 am

  Only service problem was the Service 4WD Problem as well. New module fixed problem. No other problems since. I found the ride to be very comfortable especially for a 3/4 ton. The room inside accomodates the family and kids with room to spare. 6 adults can ride in comfort with good leg and shoulder room. Milage is great for the power and weight. My average milage to-date is about 19 mpg over 17000 miles. The transmission is absolutely incredible and is what makes this truck exceptional. It handles heavy trailers with ease. I have yet to use all the power the Dmax puts out. It is without a doubt the best truck I have owned.

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  Hot Duramax - 2003 GMC Sierra 2500HD
  By J. Carroll - March 11 - 10:00 am

  This duramax is bad to the bone added bully dog 75 hp system to the truck now get 19.6 in town and 23 on the highway. pulled my 30 ft 5th wheel RV thought Colarado never missed a lick passed everything on the road and still averaged 13.7 mpg. Truck will white smoke the tires through 3rd gear and out run a new 6.0l Powerstroke no problem.

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  Duramax and Allison are superior - 2003 GMC Sierra 2500HD
  By Jim T - January 20 - 5:53 am

  I have owned this truck since new in 2003. Only in the last several years have I used it to its full potential. I have pulled a 10,000 lb fifth wheel to Florida twice and a new 12,000 lb fifth wheel to GA last week and I averaged a little over 13 mpg. On the return trip I got over 24 mpg running at 70 mph all day. I do have a tonneau cover for the bed which might help. I first took this new truck to Ohio in 2003 and only got 22 mpg with the same configuration. I did add a K and N air induction system before my last trip but this truck pulls like a champ without any additonal brains or Banks kits. The 5 speed transmssion is smooth and I know improvements have been made in the 09s.

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  8.1L tons of gas power! - 2003 GMC Sierra 2500HD
  By black dog - May 11 - 4:50 pm

  The torque and power of the 8.1L is incredible, but be aware at the gas pump. An average of 9.1 mpg will be all youll get. Towing large campers or trailers is no trouble what-so- ever. Especially in lower range gears the 8.1L begs for more. All around I love the truck, including a great interior and stock stereo.

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  Bad (good) Truck - 2003 GMC Sierra 2500HD
  By shasta33 - May 26 - 10:00 am

  Truck is great. Needs better fuel economy and a bigger gas tank. Great power and transmition (8.1 / Allison).

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  Too Much - 2003 GMC Sierra 2500HD
  By JailDoc - January 7 - 2:00 am

  The 8.1L, Allison Trans, this vehicle is beyond awesome, lousy milage but that is what was expected. Pull or tow anything, fast as hell, acceleration is neck snaping, stable anywhere you take it. So far no problems like my last GMC (ABS pump went out), the dealer is lousy, cant trust a thing they say. Time will tell.

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  dura-maxed - 2003 GMC Sierra 2500HD
  By workhorse - May 20 - 10:00 am

  I have owned my gmc for a short while and am very pleased with the Duramax/Allison combination,I have owned powerstrokes in the past,the difference is amazing, the Duramax power range extends for a much longer time, torque is great.Allison transmission holds gear going down steep grades and the mileage for a full size pickup is awesome (average is 18 mpg, I have gotten as high as 21 mpg)

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  nice truck - 2003 GMC Sierra 2500HD
  By bobby56 - August 18 - 10:00 am

  the truck is absolutely awsome. i had a 2002, same truck, traded it for the same payments and love it to death. its stong as an ox, both in horsepower and towing. (ford who?)

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  Good, bad, and ugly - 2003 GMC Sierra 2500HD
  By Ted Sparling - January 5 - 5:50 pm

  The Isuzu engine is the best part of this truck, along with the Allison tranny. The worst part has been all the GM stuff. Everything from numerous AC problems to leaks, memory features deleting themselves, multiple transfer case problems for auto 4WD, and leaking fuel injectors. If it were not for the dealerships attitude and incompetance i would buy again.

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  Nice for towing - 2003 GMC Sierra 2500HD
  By john gentry - June 19 - 6:30 pm

  This truck was bought for towing and does a great job pulling our fifth wheel camper.