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Duramax LMM

Discussion in 'Chevy Trucks' started by azandy, Oct 5, 2009.

  1. azandy

    azandy Member
    Messages: 73

    I hate to start a new thread and beat a dead horse here but my quick search didn't get me info. I've had LBZ engines before, but am looking at buying a 07 with LMM motor. I was told to expect a fuel mileage drop but wondering how much. I put a lot of miles on and would rather not get killed on fuel. Of coarse the dealer is tring to tell me it should be the same as the old ones.??? The truck is a 4x4 one ton crew. I need to decide today or tomorrow. Any help with this would be great.
     
  2. 2005_Sierra

    2005_Sierra Senior Member
    Messages: 346

    try dieselplace.com. that website is all about GM diesel's
     
  3. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    I have an 08 Silverado with an LMM. I get 14 to 14.5 with a mix of city/highway driving. If you drive 60, and NO MORE, it will get about 19 on the highway. I made a trip to North Carolina about a month ago, average speed of 70-75, it got 16 to 16.5 mpg. It's not as good as the LBZ's. It does have a ton of power, you'll like it.
     
  4. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    X2... dieselplace is cool. I go on there alot.
     
  5. GMC Driver

    GMC Driver Senior Member
    Messages: 710

    Or try duramaxdiesels.com - another great site.

    My LMM does alot better on MPG without the DPF. ;)
     
  6. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,045

    I'll agree with this. If you keep the truck for 100,000 miles you will be way way further ahead the a gas truck.
     
  7. mow 4 u

    mow 4 u Member
    Messages: 42

    I have a 08 3/4 crew at about 20k miles I removed the DPF and installed a tuner. At 70-75 mph I am now getting 20-21 mpg. The best I got was at about 60 mph 24.6 miles per gallon. Tons of power, love the truck.....
     
  8. aeronutt

    aeronutt Senior Member
    Messages: 262

    You already got great replies, but I'll add that most of the problems people experience with the LMMs vanish when the DPF does. Some people insist on EGR deletes and dead kitties too. If you don't know what that means, spend some time learning. The money you spend to set one up "properly" (even if it is illegal :() is saved back quickly in reduced repair bills and much better mileage. 21 Hwy is very believable with these simple mods.
     
  9. azandy

    azandy Member
    Messages: 73

    I thank you guys for the great info, I did pick this truck up yesterday. On the way home, about 100 miles, I got 14 mpg. Seemed a little doggy compared to my LBZ but this new truck is a dually also. If I delete the DPF, will my warranty be void? Or will the dealer overlook that if something else goes wrong? I didn't know if I should ask them or not. I bought this truck used with 12,000 miles. I was thinking of saying it was like that when I got it, but not sure.
     
  10. Newdude

    Newdude Senior Member
    Messages: 878

    Yes, deleting the DPF will void warranty.
     
  11. Q101ATFD

    Q101ATFD Senior Member
    Messages: 277

    Well, a DPF delete will only void the drivetrain warranty. The rest of the truck is still covered as long as it's under 3/36.
     
  12. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    That's true. And it wouldn't matter to the dealer if it was like that when you got it.
     
  13. azandy

    azandy Member
    Messages: 73

    I went to the dealer today to get a warranty transmission line replaced and asked them about the programming issue. The service director told me that 2 weeks ago, GM said when they pull the numbers on an LLM, they will be able to tell if it was programmed in the past. Before any warranty work can be done to any of the driveline, these numbers have to be sent for authorization. If they don't match all default, the driveline warranty will be dead for life on that vechicle.
    Not sure if I want to mess with it . has plenty of power anyway and 14-15 mpg is better that replacing something big in the future.
     
  14. badabing1512

    badabing1512 Senior Member
    Messages: 370

    X2 on thedieselplace.com, good site.
     
  15. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412


    I agree... Mine has plenty of power, and the mileage doesn't bother me. I've never owned anything that got good mileage in my whole life. I don't feel like tearing into a $50k truck for a few mpg.

    Did you have a leaking tranny line? I just had two out of the three replaced because they were leaking :mad: One of the guys who plows for me works at the local Chevy dealer and he did the warranty work. He says they'll leak again within a year... nice :rolleyes:.
     
  16. azandy

    azandy Member
    Messages: 73

    Ya right next to the radiator, The Chev dealer said this is common but hope they can figure this out soon. My truck is an 07. That's almost three years of R+D. They probably had it figured out last summer, but fired the person due to bankruptcy before production.
     
  17. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    I don't know... they've been putting the same lousy window regulators and rattly steering shafts in them for a least ten years.
     
  18. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,045

    My personal LMM has Straight turbo back exhaust and I took off the EGR motor and cooler and replaced it with a new straight pipe, my dealer has seen it all and they havn't red flagged my truck yet but I don't expect warranty do to power upgrades. My other LMM is bone stock and it's a work truck, I don't screw with things that make me money.

    I might have a few other things done do it also that might void the warranty.

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  19. GMC Driver

    GMC Driver Senior Member
    Messages: 710


    Chicken Sh*t!



    :laughing: