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Whose got the 8.1, Allison combo?

Discussion in 'The Garage' started by mtrdrms, Feb 16, 2006.

  1. mtrdrms

    mtrdrms 1/2 ton status

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    On your new chevy truck? I was just wondering what gas mileage you were getting? I am seriously looking into a beauty of an 2002 but I have a 20 mile commute. Thanks.
    Andy
     
  2. dwoods

    dwoods 1/2 ton status Premium Member

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    Friend says about 10 mpg.
     
  3. 78Buford

    78Buford 1/2 ton status

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    I don’t own an 8.1/Allison truck, but have some info. A friend of mine recently bought a 2002 GMC 2500HD 4 door, longbed, 4x4, loaded, leather, etc, with the 8.1 and Allison trans. It cost $17.5K, and had 101K miles on it. He had the previous owner/dealer fib a bit & stated that it had 99.5K miles on it (had to be under 100K for the warranty offer) and bought a very good warranty…I don’t know the exact details, but it covers most everything on the truck (drivetrain, electrical stuff like power windows, etc) for a long time. Right after he bought it, he had problems with a front wheel bearing, and the warranty took care of everything. I’ve ridden in it a couple times, and drove it for an hour & a half a week ago…mostly interstate.

    He does construction work & puts a lot of miles on it. He stated that everyday driving it gets about 8 mpg. On the interstate with the cruise set around 70 mph, he has gotten 12.5-13 mpg out of it on long trips.

    I only stomped on it a few times. It feels very torquey on the interstate at 70 mph @ 2000 rpm in OD (it has 33” tires)…barely touch the throttle, and it accelerates well.

    I stomped it from a 5 mph roll and held it at WOT through 1st & through most of 2nd gear. The 1-2 shift happens with an odd-yet-kinda-cool “blipping” sound. It actually felt like it accelerated faster in 2nd gear than it did in 1st, likely due to the low revving engine. WOT upshifts are around 4400 rpm.

    Damn nice truck….even if it is a GM. :D

    Roy
     
  4. Goose

    Goose 1/2 ton status

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    My friend pulls his bass boat with it about twice a month. Gets 13mph from Wichita to the Ozarks and back.

    Loves the Allison.
    Loves the power of the 8.1
     
  5. IGOR

    IGOR 1/2 ton status Premium Member

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    I have one but it's in a GMC (I suppose that counts)

    Mine is a short wide 2002 GMC. I love the 8.1 - but I hate the mileage - 8 or 9 is what I'm getting around town - I concur about around 12 - 13 on the highway -

    I think if I were to do it over - I might go with the Duramax - just to get the mileage gains - plus just for the cool factor...
     
  6. 84K5BD

    84K5BD 1/2 ton status

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    i have an 2001 ecsb 8.1 allison with 3.73's. i have a fabtech 6 in. lift with 35's. on the highway doing between 65-70 i can get about 13.5mpg. around town 9-10, that's empty. towing my k5 on my 22ft. trailer, which has a combined wieght of around 18'000 lbs, i get about 9-10 on flat roads and around 7-8 thru the mountains. my mileage stayed about the same after installing the lift and tires when it was empty but when i am towing it went down some to what it is now, i am regearing my truck in the spring to 4.56's. i have done a power programmer, dual 3in. exhaust and mobil 1 synthetic fluids in diff's, tcase, and engine.
     
  7. MT wheeler

    MT wheeler 1/2 ton status

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    As is the consencous with everyone else I too get 10mpg in town and 13 on the freeway in my 2002 4X4. Loaded or not. If you are considering buying one of these trucks don't buy it for the gas milage buy it for the power. I love my truck and I am totally content with the milage.:D
     
  8. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Check over at the sister site www.towrig.com There are a few 8.1L GM guys over there.

    I've heard mainly all good about the engine, except for some odd oil consumption on earlier models.

    It's a big block.....good power but not so good for mileage.:wink1:
     
  9. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Be carefull with some of the service contracts. I was told by the dealer that I bought my truck from that the service contract would replace just about anything. I went ahead and purchased the contract for $2k.

    I had a problem with my heated seats....read the fine print...not covered. Had multiple A/C problems....."a part has to FAIL for us to cover anything." An A/C system with no freeon doesn't count as failed.:rolleyes: I got to pay to have it charged up so they could find the leak later and figure out what failed.:rolleyes: Then.....there is little things they throw in that they don't cover. They would cover everything except for the orifice tube in the A/C system.....you need the whole line when you replace the orifice tube....I got to pay for that....

    They cover stereos...the deck, the wiring....but not the actual speakers, meaning no replacement on my passenger speaker that pops every now and then.:rolleyes:

    I got $2,400 out of them for my new built tranny though!

    What I am trying to say, is most warranty companies are picky. They are for good reason though...if they werent and just handed out repair work they would be broke. You just have to decide if it's worth the money for the contract and if it's worth doing a little phone fighting every time it goes in the shop.

    I figured that I would either loose the tranny or the main injection pump in my Ram Cummins since these two items are weak spots in the Dodges, both being VERY costly. Thats why I opted for the contract. I did loose the auto trans and all in total I have got nearly $4K back out of them between my trans, a bunch of A/C work, and a lift pump in the last 2 years. But....it was a hassle to get every dollar.
     
  10. BrandonW

    BrandonW Registered Member

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    I have the 8.1 in my Suburban. It has the 4l80e and 4.10 rear end. 8mpg to 8.6mpg and thats it. It also drinks oil. Good power though. Im looking into a new computer to get rid of the torgue managment though.
     
  11. rlhenry

    rlhenry Registered Member

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    I've got an '01 with the 8.1 and the Allison with 4.10 gears. 6" lift, 295's (because I got 10" wide Centerlines so anything bigger rubs too much). I also have a Gibson cat-back system, Volant air-intake, and Hypertech programmer. I get anywhere from 9 to 13 mpg depending on load and type of driving. Let's just say I didn't get it for the mileage, but it's a lot of fun to drive. To make matters worse, I programmed it for 91 octane fuel. All this may explain why it only has 27k miles on it.....
     

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