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05 Sierra SLT question on gearing.

Discussion in 'GM Powertrain' started by Sierraowner5.3, Apr 19, 2011.

  1. Sierraowner5.3

    Sierraowner5.3 Rockstar 3 Years 1000 Posts

    I was wondering how to check what gears I have, and depending on what I find, what is a good rear end to have. Reason I asked is this truck runs at 1800 rpm or so running down the highway at 70, wereas the silverado i used to have ran just a hair over 2000.

    wondering if I have 3.43 vs 3.73

    thanks in advance.

    Alex
  2. 99'HEARTBEAT

    99'HEARTBEAT Epic Member Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    The way to find out What Gears you have......In your Glove Box is a White Sticker and on it....you will see the Trucks Vin # and a Series of Letters and Number's,those are RPO Code's....Which stands for Regular Production Options....In Short it what your Truck came with from the Factory.

    To find out what Gears you have you will be looking for one of the following,

    GU5.......3.23
    GU6.......3.42
    GT4.......3.73
    GT5.......4.10


  3. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    You may have 3.23's.
  4. Sierraowner5.3

    Sierraowner5.3 Rockstar 3 Years 1000 Posts

    just went and looked, got the 3.42s. if i were to change em, what would be better, 3.73 or 3.90s?

    Alex
  5. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    depends what you are planning on doing. 3.73 are the prefered gear in my book. they offer the best for highway, and towing at the same time. You go any higher and you are drinking fuel any lower and you dont have any power when you need it towing.
    now that is running the stock truck or close to it.
  6. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    X2, I'd go with the 3.73's.
  7. Sierraowner5.3

    Sierraowner5.3 Rockstar 3 Years 1000 Posts

    well, what would swapping to 3.73s cost? im planning on doing a front end level, but not jacking it up any, a size larger tires may find there way on there at some point, but im not planning on lifting or putting 35s under it. gas costs to damn much.


    Alex
  8. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner Gold Member 1000 Posts

    since you would need to do front and rear gears with a 4x4 you are looking around $1200-1500 (maybe a little higher depending on place brand etc). I would also recommend the 3.73 with what you are suggesting as upgrades and driving.
  9. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    IF you arent planning anything drastic, then stick with the 3.42s since the cost wont pay for itself. especially if you use the truck more as a commuter than anything else.

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