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NP205 Low Range - What's the ratio?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Greg72, Nov 15, 2001.

  1. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    NP205 Low Range - What\'s the ratio?

    Checked the archives with all the relevant keywords that I could think of... no dice.

    When in 4LO what is the effective reduction ratio for the box? I'm guessing something like 1.75:1 or 1.90:1 but I don't know for sure.......

    Anyone? Thanks..... [​IMG]

    -Greg72
     
  2. arq

    arq 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    1.96 to 1

    ARQ.

    offroad baja!!!
    72 4x4 CST Blazer
    71 4x4 CST Blazer
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  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: NP205 Low Range - What\'s the ratio?

    This board is amazing!......an answer to almost any question in less than 60 seconds! [​IMG]

    THANKS ARQ!

    -Greg72
     
  4. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Re: NP205 Low Range - What\'s the ratio?

    Close, its 1.98:1. Hey if I didn't point that out EX would have.

    Jim '80 GMC & '73 Blazer
    Body by Tellico
    <a target="_blank" href=http://www.tellicok5.rockcrawler.com>www.tellicok5.rockcrawler.com</a>
     
  5. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    Actually ARQ had it right, if you look at the Specs section of CK5 it lists the low range as 1.96:1..

    Mike

    <font color=green>"1024x768x256... Sounds like one mean woman."</font color=green>

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  6. zakk

    zakk 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    1.96:1 and np203's are 2:1

    -Zakk
    '77 K5 SB 400 TH350 NP203 p/t 6" Lift D60 14BFF 4.10's 36"Wrangler II's

    [​IMG] CK5's MOAB 2002 OR BUST!! [​IMG]
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: NP205 Low Range - What\'s the ratio?

    .....so far my highest bid is at 1.98:1 ..... can I get an offer at 1.99? Anyone....ANYONE! [​IMG]

    For the purposes of calculating my "Crawl Ratio" I don't think it's going to matter much either way it turns out..... By the way, don't bother asking what it turned out to be......it looks more like a hockey score than a crawl ratio! [​IMG]



    -Greg72
     
  8. zakk

    zakk 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    LOL!
    mine is 20.08:1
    terrible, isn't it!?

    -Zakk
    '77 K5 SB 400 TH350 NP203 p/t 6" Lift D60 14BFF 4.10's 36"Wrangler II's

    [​IMG] CK5's MOAB 2002 OR BUST!! [​IMG]
     
  9. 1979Jimmy

    1979Jimmy 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    Mine is 20.88:1 not too bad considering the only gearing thats been changes is in the differentials.

    79 Jimmy, 5" lift 35 M/T with a 383 puttin out 400hp and 450lb/ft. Locked front and back.
     
  10. michaelm

    michaelm 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    35 teeth / 25 teeth = 1.4

    times

    35 teeth / 25 teeth = 1.4

    = 1. 96

    did i get that correct?
    dont see how the 1.98 number can pop up unless i miscounted the teeth
    need a disassembled photo to help with the math?
     
  11. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: NP205 Low Range - What\'s the ratio?

    Zakk,

    Don't forget you have an automatic like me....so you get an extra 3:1 multiplier at low RPM. The stick-shift guys have a much lower 1st than we have on the TH350, but the effect of the torque converter kinda makes up for it.

    I think the corrected 1st gear ratio for a TH350 is 2.52 x 3.0 (the correction factor) = 7.56 "effective 1st gear low-RPM crawl ratio"

    If this is all wrong don't blame me, blame the July 2001 issue of "Four Wheeler".....they're the ones who told me!! [​IMG]

    -Greg72
     
  12. RedDwarf

    RedDwarf 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    NP 203 ratio is 2.01:1, not 2:1. If you really cared, you would have known this! [​IMG]
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: NP205 Low Range - What\'s the ratio?

    32.74:1 for me right now.
    52.63 very soon.


    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  14. Donovan

    Donovan 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    You are correct it is 1.96 to 1. The teeth are 35 and 25 on all the gears.

    Donovan
    <a target="_blank" href=http://www.rustbucket.rockcrawler.com>www.rustbucket.rockcrawler.com</a>
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  15. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    Dear Lord, I saw the topic of this post and the number 1.96:1 popped in my head with out a moments hesitation. I've never even seen one in real life, outside of the shifters in two trucks. God, I need a g/f, haha [​IMG]

    "I ain't nobody, dork."
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  16. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: NP205 Low Range - What\'s the ratio?

    It's sad isn't it......some people can recite all the gear ratios, part numbers and obscure factoids about their K5......but ask them when their wedding annivesary is and you get a blank stare! [​IMG]

    Gearheads are a special breed.

    -Greg72
     
  17. michaelm

    michaelm 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    not me,
    i cheated and met her on Halloween, and married her on Oct 13. easy to remember....her birthday is another story though, yikes. least i remember she is a 72 model
     
  18. 1979Jimmy

    1979Jimmy 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    Are you guys serious about that 7.56 1st gear ratio. I have a 79 Jimmy with a turbo 350. Would my final ration really be 61.52:1?

    79 Jimmy, 5" lift 35 M/T with a 383 puttin out 400hp and 450lb/ft. Locked front and back.
     
  19. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: NP205 Low Range - What\'s the ratio?

    Before the torque convertor hits stall the effect is more like 1.8 to 1, not 3 to 1. So under 1800 rpm your crawl ratio is better than above 1800 or so. Pretty hard to stay under the convertor stall in low range though. Using this logic we should all get 5000 RPM stall convertors and go crawlin'[​IMG]

    Crawl ratio should be figured out based on the actual gear ratio's IMHO.

    Rene




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  20. 1979Jimmy

    1979Jimmy 1/2 ton status

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    Re: NP205 Low Range - What\'s the ratio?

    so what would my real crawl ratio be?

    79 Jimmy, 5" lift 35 M/T with a 383 puttin out 400hp and 450lb/ft. Locked front and back.
     

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