Duramax 6.6 Diesels, All the same block?

Discussion in 'Trucks and Trailers' started by RickyDL77, Sep 4, 2014.

  1. RickyDL77

    RickyDL77 LawnSite Senior Member
    Posts: 431

    We have 2 2007 GMC C4500s both have the LMM 6.6. One broke a crank, the other we are about to tear down and see what broke. Both had the Harmonic Balancer come apart and reek havoc. Both plus a 2004 with in a 2 week span, the 2004 managed to go without damage internally... Dealer says there are no recalls or service bulletins pertaining to this matter.

    We just got a long block for the first truck that broke the crank, installed it 2 weeks ago and can not get it to start on it's own, it will fire with either. Called the local Truck shop that deals with Duramax and he pointed me to a pain in the arse priming process, after a week we started looking into other things like internal timing not being right for the computer. I pulled the paper work, and called the dealer for which engine belongs to this truck. Dealer says its the mid year 2007.5 model having the newer LMM engine setup. They place we got the engine send us the Long Block labeled LB7. I have talked to the sales/mechanic that sold us the long block and he told me the LMM, LB7, LBZ, and 1 other all share the same block. Only difference are the computer detuning, possibly turbo, emmisions, and sometimes the heads and intakes.

    Anyone with Knowledge on Duramax's please lend me some info as to whether this is correct or not. If it is correct, point me in some type of direction to look.

    The mechanic working the job has 7 different codes, starting with Cam sensor, then crank sensor, intake temp sensor, airflow, and 3 others that he says did not matter, prolly just set off from any one of these. we transferred all parts from original engine which was not having any issues...Also replaced the cam and crank sensors because of the original internals busting loose.
     
  2. Chris_NC06

    Chris_NC06 LawnSite Fanatic
    Male, from Sanford, NC
    Posts: 6,761

    No, they aren't all the same. The LB7 and LLY ('01-'05 MY) use the same block. The LBZ and LMM ('06-'10 MY) use the same block and the LML ('11-current MY) has a different block. The LBZ/LMM and LML blocks are supposed to be stronger, but a lot of race builds use and LB7 block for whatever reason. Most parts on the Duramax engines are interchangeable.
     
  3. RickyDL77

    RickyDL77 LawnSite Senior Member
    Posts: 431

    Awesome, thanks for the quick response.

    So are the internal timings different between the LB7 and LMM? he did mention that there were 2 different blocks but the only difference is 1 extra bolt on the front cover... I'm no diesel mechanic, I just work the office in the shops, used to run the small engine shop here till they needed my skills elsewhere. He also said there was pretty much only 1 cam for the 6.6..does that hold true?

    I'm planning on calling the dealer again this morning to verify, and have more than my theories to show the guy that he may have given us the wrong engine... he was pretty stern saying" I have sold over 1000 6.6 duramax's and never have heard of such a thing... lol
     
  4. Chris_NC06

    Chris_NC06 LawnSite Fanatic
    Male, from Sanford, NC
    Posts: 6,761

  5. WayneJessie

    WayneJessie LawnSite Member
    Posts: 203

    Get the air out of the injection system and it'll run. Most any decent shop should have Alldata online that'll give you the step-by-step procedure for purging/priming the fuel system.
     
  6. RickyDL77

    RickyDL77 LawnSite Senior Member
    Posts: 431

    We got it going... The mechanic doing the repower forgot to transfer the pickup plate for the cam sensor.. fun stuff.
     

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