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Question??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by UseYourBlinker, Jun 16, 2000.

  1. UseYourBlinker

    UseYourBlinker 1 ton status

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    Hello again...How can you tell what size gears you have in a corporate 10 bolt on a 84K5 Blazer? I need to get some gears for it....should I get 3.73 or 4.11? The Blazer has 2.5 lift with 33 inch swampers....I want to install a 4 inch lift in the future....thanks for any info!
     
  2. getsome

    getsome 1/2 ton status

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    I'm not sure about what gears you have but on my 84 with a 6" lift, 35" BFG's, and 4.11 it's a dog when it hits 4th gear. When I put new axles in i'm going to change to 4.88's. You can afford to go with taller(numerical) gears then if you had a th350. I'd go with the 4.11 with the 33's. Go to 4lo.com and check out what they have to "say" when you plug in the numbers.

    Getsome
     
  3. Topher

    Topher Registered Member

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    If your drivetrain is stock and you have a 700r4 trans & np208 t'case then you might have 3.73's like my '85. If you don't want to pull the diff cover to count the teeth on the ring & pinion gears then you can make a mark on the tire and one on the driveshaft. Then rotate the tire one full revolution and count how many times the driveshaft turns. This'll give you an indication of your gear ratio; if the driveshaft turns about 3 3/4 times for a single revolution of the tire then you know you have 3.73's.

    My truck came stock with 3.73's & 31" tires. I've been running 33's for years and never liked the performance decrease (it's amazing how 2" can make a noticeable difference). I knew I was gonna lift it and swap in larger tires someday so never bothered to upgrade the gears. A 4" lift is going on pretty soon and I'm picking up an axle w/ 4.56 which should be good for the 35" or 36" I want to run. It should provide good low end throttle control & acceleration when 'wheeling while retaining a suitable cruising RPM on the highway with my overdrive trans.

    Hope this helps some.

    Chris
    85 & 78
    ...one's running...both need work
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Look at the sticker inside the glovebox. It will list all of the options that came from the factory on that truck. Some years list the RPO (Regular Production Option) codes and the description but somewhere along the way GM started to just list the RPO codes. There's a section in the front of the factory service manual that lists all of the RPO codes and tells you what they mean.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  5. Executioner

    Executioner 1/2 ton status

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    This is not correct if you have an open, limited slip, or locked diff.
    So what type of diff will it work on ?
    Think about please post back
     
  6. Corey-88K5

    Corey-88K5 1/2 ton status

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    Home: Michigan, Stationed: Hill AFB (Home of Moab.

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