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5.13 Gears

Discussion in 'The Garage' started by scoutillac, Mar 3, 2004.

  1. scoutillac

    scoutillac 1/2 ton status

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    Are 5.13's too low for 39.5's pushed by a stock TBI 350, 700R4, NP241?
     
  2. BranndonC

    BranndonC 3/4 ton status

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    no no no! i have 37's and the same setup and love it, would even like it with 35 or 36's, i can currently do 80+ on the freeway and have a 50ish crawl ratio /forums/images/graemlins/woot.gif
     
  3. scoutillac

    scoutillac 1/2 ton status

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    [ QUOTE ]
    no no no! i have 37's and the same setup and love it, would even like it with 35 or 36's, i can currently do 80+ on the freeway and have a 50ish crawl ratio /forums/images/graemlins/woot.gif

    [/ QUOTE ]
    What kind of RPM's are you turnin at 80?
     
  4. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    5.13's are barely low enough for a th700 and 39.5's! /forums/images/graemlins/eek.gif
     
  5. BranndonC

    BranndonC 3/4 ton status

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    3000-3150 i'd say at 80
    65 MPH is 2400 RPM
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    5.13 is the answer to every gear related question. /forums/images/graemlins/thumb.gif
     
  7. scoutillac

    scoutillac 1/2 ton status

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    Well I'm not nervous about it anymore. Now I just need a Detroit for poor mans wages. I got a set of backing plates, a set of hubs with lockouts, a spare spindle, and a spare rotor to finish my 8 lug conversion for 20 bucks. SCORE!!
     
  8. Hossbaby50

    Hossbaby50 3/4 ton status

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    If I had it to do over i would have regeared my axles to 5.13 instead of 4.56's like I did. I run 35's now and with I had 4.88's or 5.13's. When I step to 37's or 38's I might seriously look into regearing again.

    I run a 350/700r4/208 setup.
     
  9. scoutillac

    scoutillac 1/2 ton status

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    If I knew how to set the gears myself I would redo my Burban again, but with 3/4 ton axles. I have to pay someone to do my stuff. I have to thank my wife, after beating her, for rolling the 90 Blazer I built for her. My buddy thanks her too. He bought all the interior and the entire front clip for his 82' Blazer. I did keep the drivetrain for the scout though. Fresh rebuild-952 miles on it.
     
  10. FRIZZLEFRY

    FRIZZLEFRY 1/2 ton status

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    [ QUOTE ]
    5.13 is the answer to every gear related question. /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    It wasnt the answer for me /forums/images/graemlins/tongue.gif
     
  11. tecton

    tecton 1/2 ton status

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    when you regear, you just change the r&p right?
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    [ QUOTE ]
    5.13 is the answer to every gear related question. /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    It wasnt the answer for me /forums/images/graemlins/tongue.gif

    [/ QUOTE ]

    That's because you have a '70 rear. In that case, the answer to everything is 7.17s.
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    when you regear, you just change the r&p right?

    [/ QUOTE ]

    Typically rebuild the axle at the same time.

    For some axles that have carrier breaks, you might have to replace the carrier to put the gears that you want in them.

    If you're installing a locker at the same time that's no biggie though, a detroit replaces the carrier and you can get them for all different gears.
     
  14. tecton

    tecton 1/2 ton status

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    on a scale of 1-10, say....1 is building a lego truck and 10 is building an entire truck, how hard is changing gears?
     
  15. zakk

    zakk 1/2 ton status

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    [ QUOTE ]
    Are 5.13's too low for 39.5's pushed by a stock TBI 350, 700R4, NP241?

    [/ QUOTE ]


    The 5.13 Manifesto

    [ QUOTE ]
    Zakk’s Dissertation on why 5.13’s are the best choice for a 700R

    Recently, I made the switch to 5.13’s in my D60/14B combo. I run a mildly build TH350 and 39.5” TSL’s. The 4.10’s I did have were killing everything: the motor, the trans, freeway “ get up” …all of it was terrible.

    So, after typing this up a few times, I will commit this document to the annals of time, and have a friend of mine host it.

    The problem with larger tires and a 700R and larger tires, is that you can’t seem to get enough RPM’s to get the OD to properly engage.

    Dr. Watson of ORD fame has this problem with the Art Carr 700R and his 42’s. There is just not enough RPM’s to shift in OD. So what little freeway driving he does do, is all done in Drive.

    When we mix this with tires in the 35-38” range, 5.13’s are a great choice.

    Assuming a true tire dimension of 35”, a vehicle with a small block motor mated to a 700R would spin 2241 RPM’s. Running with 4.88’s would have the engine humming along at 2132 RPM’s, only saving 109 revolutions of the motor per minute. All are calculated at 65 MPH.

    Assuming a true tire size of 37”, 5.13’s would net 2120 RPM’s at 65 MPH.

    Most small block motors are comfortable running between 1800 and 2800 RPM’s. 5.13’s with the addition of OD allow this number to be on the lower end of the spectrum, while allowing for maximum acceleration and off road performance. Gearing can make a motor that is slightly lighter on power really come alive, as I have found with my mild small block 350 with approximately 285HP at the flywheel.

    In closing, unless you bought your axles with 4.88’s already installed, there is no reason that this author sees to not go with 5.13’s from your present gear ratio.

    Let the flaming begin….


    [/ QUOTE ]
     
  16. Derf00

    Derf00 1/2 ton status

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    I agree. I thought 5.13's would be to low for our 700R4 and 38's, but it only took about 2 min driving to figure out they were great. One other factor that we all forget when trying to decide on gears is the weight of the larger tires. I am running 38" SSR's with alum wheels, you pick up one of those and your kids will definately be born baldheaded and naked, can't imagine how heavy 40"+ tires and wheels are.
     
  17. Derf00

    Derf00 1/2 ton status

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    Re: 5.13 Gears *DELETED*

    Post deleted by Derf00
     
  18. zakk

    zakk 1/2 ton status

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    i was so right you had to post it twice /forums/images/graemlins/smile.gif /forums/images/graemlins/waytogo.gif
     
  19. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    i was so right you had to post it twice /forums/images/graemlins/smile.gif /forums/images/graemlins/waytogo.gif

    [/ QUOTE ] /forums/images/graemlins/histerical.gif
    I'm debating between 4.88's and 5.13's with mine on 35's. I'm thinking 4.88's only because my 406 makes lots of low end and doesn't like to wind up, plus I tow a lot in direct drive and don't wan't the motor screaming.
     
  20. zakk

    zakk 1/2 ton status

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    didn't you read my post!?

    5.13's!
     

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