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What R&P ratio?!?

Discussion in 'The Garage' started by SubYuman, Aug 28, 2002.

  1. SubYuman

    SubYuman 1/2 ton status

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    C2500 Suburban with 454 on 37's and a 4L80E.
    4.11? 4.56?
     
  2. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> 4.56 or 4.88</font color>
     
  3. little79k5

    little79k5 1/2 ton status

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    i'd go 4.56
     
  4. bablazer73

    bablazer73 1/2 ton status

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    4.56. i would lean towards 4.88's
     
  5. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Depends what you want to do w/ it.
     
  6. SubYuman

    SubYuman 1/2 ton status

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    Was running 31's when I saved it from a fate worse than rust.... he was about to SLAM it...bags to the GROUND.
    After the spindles, the LONG coils and body lift (long travel coming soon) I got the Hummer tires from a guy who needed to save $$ on his taxes, so he re-fitted his Ford with new Goodyears.. got them for a case of Becks beer.
    I tow a 29' Catalina sailboat (4500 lbs.) The new roller rockers added a bit of pep, but the Sub HATES to climb hills now.
    I drive on the beach a lot, but most of miles these days are to the West Marine store for parts, so it is a on road life for now. 60 is as fast as you can go here in Hawaii, so too fst isn't an issue.
    What's the RPM to tire height/rp ratio formula? RIght now, at 60, I turn the 454 at 1600 rpm.
     
  7. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Ok, now we can do some figguring. I would go w/ at least a 4.88 &amp; maybe 5.13 in your situation. Here is why; I am still making some assumptions, #1 a 14B rear, you have enough strength to handle the small pinion. #2 HI is full of mountainous roads, the lower gears will help with climb and save your breaks on the way down. Now for the part we know are fact; #1 your topping out at 60 MPH, #2 you have O/D, &amp; #3 your pulling a heavy load. All of these beg for lower gears. If you were to go over to www.4lo.com you would be able to see that w/ 4.88s in drive you will be turing under 2700 RPM @ 60 MPH or w/ 5.13s you could be under 2000 RPM in O/D. You said "C" so 2WD, right? If so I would go w/ 5.13s due to no low-range. If its 4X4 I would go w/ 4.88s to help keep the 10B alive.
     
  8. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I agree with Bigbear. You've got a 4L80E - don't just carry it along for the ride, USE IT! Go with the 5.13's, it'll feel real nice.
     

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