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Thread: '99 2500 6.5L to Duramax Conversion

  1. #1
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    Default '99 2500 6.5L to Duramax Conversion

    I have a low mileage '99 Suburban with a 6.5. I saw the discussion of the conversion to Duramax, but it said it was intended for only the '88-'98 models. Am I correct in thinking that the difference would be in the dash-instrument cluster only?

    Thanks

  2. #2
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    It depends on the body style you have, GMT-400 or GMT-800. 1999 was a transition year, and I don't recall how the Suburbans were released, if they were a half-year release, or if there was a difference between the weight classes. 2001 was the first model year for the Duramax. GM has always found a way to defy any direction of logic during these times. A GMT-800 (1999+) would be the simplest, with very little accommodations to consider.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    Quote Originally Posted by DmaxMaverick View Post
    It depends on the body style you have, GMT-400 or GMT-800. 1999 was a transition year, and I don't recall how the Suburbans were released, if they were a half-year release, or if there was a difference between the weight classes. 2001 was the first model year for the Duramax. GM has always found a way to defy any direction of logic during these times. A GMT-800 (1999+) would be the simplest, with very little accommodations to consider.
    Thank you. Would you happen to know how I can tell the difference? From what little reading I've done, I'm guessing mine is a GMT 410.

  4. #4
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    I suppose I was asking the question. Which do you have? I simply don't recall what GM did during that transition, and I don't know what the equipment and RPO stickers should show to determine it. As sure as the sun rises, when you have it all figured out, an odd duck will show up. If yours looks like previous 1990's models, then it's a 400. If it looks like more modern models up to 2006, then it's an 800. It's important to the simplicity because a later model will fit the instruments and harnesses you'll need, rather than shoehorning everything. Look at the panoramic picture at the top of this page. Which grill looks like yours? The trucks on the far left and right are GMT-800 trucks, with different models mixed in between. Lil' Red is a GMT-400.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

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