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Gearing question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bad_bo_ti, Jun 7, 2000.

  1. bad_bo_ti

    bad_bo_ti 1/2 ton status

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    I plan on running 38 in tires, i have a 14 bolt ff and an 8 lug ten bolt. what gears should i run for mostly daily driving, i was thinking 4.56s, but i dunno, the axles right now have 3.73s in them, what gear ration would bebest?
     
  2. HarryH3

    HarryH3 1 ton status Author

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    Depends on the tranny you're running. If you have a direct drive high gear, then I'd go with the 4.56's to keep the engine from screaming on road trips. If you have an overdrive tranny then you can easily get away with 4.88's.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <font color=blue>http://ThunderTruck.ColoradoK5.com</font color=blue>
     
  3. ggallin13

    ggallin13 1/2 ton status

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    Would 4.88s be better for crawling only, or are there other benefits that lower gearing would offer? Beyond that, wouldn't the motor rev higher even with overdrive?
     
  4. HarryH3

    HarryH3 1 ton status Author

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    If you have overdrive and gear too high, you won't be able to use the overdrive gear. It will make the engine turn too slow at legal speeds. [​IMG] Small blocks don't like to cruise at much below 1,800 RPM. A big block might be OK, since it would be near the torque peak at that RPM, but most small blocks will prefer to be in the 1,800-2,200 RPM range while cruising.

    The .70:1 overdrive ratio in a 700R4 will make those 4.88's behave just like 3.41's (4.88*.7) when in high gear.

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

    Balou 1/2 ton status

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