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OT GMC 3/4 ton Diesel

Discussion in 'Uncategorized Threads' started by chopperman, Jun 16, 2008.

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  1. chopperman

    chopperman Member

    Joined:
    Feb 12, 2006
    Messages:
    48
    What can anyone tell me good or bad about Gmc 3/4 ton diesel with Allison transmission? Chris
     
  2. Tom Strunk

    Tom Strunk Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    1,309
    Location:
    Payson, Arizona
    I've had two, a 2003 and a 2006. Both excelent trucks, great power and fuel mileage. Both of mine averaged around 17.5 around town and 20 on the highway. I have a Magnaflow 4 inch cat back exaust and a PPE programmer on my 06, I have a boost and exaust gas temperture guages on my truck. I usually set the programmer on tune 1 for towing and tune 2 for everyday driving.

    I like the newer ones with the 6 speed trans the best.


    Tom Strunk
     
  3. chiefjon

    chiefjon Active Member

    Joined:
    Jan 29, 1998
    Messages:
    1,376
    Location:
    El Dorado Hills, CA
    I have an 04 Chev with the same equip. I pull a 30 5th wheel and by letting the computer drive the thing, it gets great mileage and has more power than I need. No problems at all with the rig. I will start driving it again when the cost of diesel in CA drops considerably below $5.50. Crap...

    JON
     
  4. ec90t

    ec90t Guest

    Chopperman,

    If you are looking into one new or used make sure of the gearing. 3:73's are plenty unless you are hauling more than 15,000 lbs. The 4:10's tend to be a little harder on fuel. Other than that, they are great trucks.

    ec90t
     
  5. stu42

    stu42 Member

    Joined:
    Apr 24, 2007
    Messages:
    92
    I have a 2006 GMC diesel with Allison 6 speed, I am getting terrible milage. Put on Magnaflow's best stainless steel 4 inch exhaust with AFE's best filter system - snorkle and Progard filter. Milage went from 11.7 to 12.3. Have had it back several times to the dealership in Placerville, Calif. where I purchased it and the service manager says "That's about right!" I am getting the worst fuel economy of anyone I talk to. Oil change delo every 3 thousand and new filter at 15. With diesel fuel in this area running $5.15 plus per gal. it is beginning to peeve me. Any thoughts! Stu
     
  6. H82MIS

    H82MIS TS Member

    Joined:
    Jan 29, 1998
    Messages:
    2,052
    05 Duramax, 5 speed Allison, stock exhaust, K&N cloth filter, 3:73 gears, Stanadyne Performance fuel additive,, 23 MPG hiway,,Why ?? "DRIVE 65",
    When I drive over 70 it all goes to hell,,
     
  7. Chango2

    Chango2 Active Member

    Joined:
    Nov 12, 2007
    Messages:
    3,518
    07 Duramax Chevy here. 3/4 ton, extra cab, 4x4. On Fwy, no trailer, keeping it under or at 65 mph, 19-20 mpg. Towing travel trailer, 21 foot, 4600 lbs. with all gear and water etc. got as much as 15.5 mpg L.A. to Vegas, but usually 14.4-14.5 mpg ovrall when towing. 14-16 mpg in mixed town driving. I avoid that.

    Mileage takes a huge dump over 65 mph...pushing too much air. I added Banks exhaust and snorkel type intake. Picked up a little more throttle response, but, more importantly, runs slightly cooler and mpg went up 10%. That's a 50 cts. per gallon savings these days..

    But..bottom line, great truck, recommend, I try not to drive it too much now given the cost of diesel,use truck mostly on fwy or to tow these days.

    Highly recommend vehicle if you need a tow rig. Refined, sophisticated, plenty of power, comfortable. Love the Allison. I feel this about diesel trucks: Ford makes the nicest truck. Dodge the best engine for towing. Chevy/GMC make the most powerful and best all-around engine, fastest stock truck, most car-like truck. I'd like, given all choices: Dodge engine in a Ford truck with an Allison trans!!!

    Chevy/GMC is the best all-arounder and the fastest and smoothest stocker.
     
  8. noknock1

    noknock1 Active Member

    Joined:
    Jan 29, 1998
    Messages:
    1,399
    Location:
    Stranger in a Strange Land
    I've got a 2003 GMC duramax and have had zero issues with the exception of one. The air conditioner doesn't freeze you out like the other GM products I have driven over the years.

    I took it in twice to the stealership and was told that 65 degrees is fine. 65 degrees on a 90 degree day with high humidy takes a long time to get the cab cool.

    Regardless there is a service bulletin that addresses the problem and I am going to try a second dealer, just haven't made it since it is 40 miles away.

    When dealing with warranty issues it will be hit or miss with any brand of diesel truck.
     
  9. TEXASBEN

    TEXASBEN Member

    Joined:
    Jan 29, 1998
    Messages:
    64
    Have an 07, Classic body, Duramax, Allison, love the truck, is used every day to tow boats to the lake for testing. Also do some custom towing boat deliverys i/e long hauls pontoons and day cruisers great power and nice fuel eco. Around town 12-14 mpg, highway@65 mph gets 19.8 mpg, traveling fast 75-80 mph will get 16-18 mpg, my wife loves the nice ride. Crew cab short box, with 3:73 ratio, I had a Power stroke f-250 1999 drove it 368,000 miles also a great truck, I dreive about 36-38,000 miles a year. I upgraded the muffler and put 265 tires on, no chips as of yet, but soon.

    Ben Dobson
    TexasBen
     
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