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700R/208: Poor Man's doubler?

Discussion in 'The Garage' started by zakk, Feb 5, 2003.

  1. zakk

    zakk 1/2 ton status

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    700R/208: Poor Man\'s doubler?

    I have been reviewing the recent trip to Frank Raines, and my rig is grossly under geared.

    Let's compare:

    Zakk's rig:
    TH350/NP203/4.10's/39.5" TSLs = 41.5:1 Crawl Ratio

    Rod's Rig:
    700R/NP208/5.13's/42" TSLs = 82:1

    Chris' Rig:
    700R/208/3.73/33" Interco Truxs(?) = 60:1

    Now, if I have already come to grips that I need 5.13's. But now, the tranny/t-case combo looks suspect.

    If I add a doubler and 5.13's (that would cost around $3,000 for both mods) my crawl is up to 102:1

    But Rod's Rig has a 82:1 after only going to the 5.13's!

    Maybe I am comparing apples to oranges. But a swap to a 700R/208 with new driveshafts and everything else would still run around $3,000.

    Thoughts?
     
  2. Greg72

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

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    Re: 700R/208: Poor Man\'s doubler?

    Well for starters.....you can remove the tire diameters from the question. Crawl ratio is a straight mathematical "gear reduction" type thing....tire diameter may affect highway rpms, etc.. but it won't change a crawl ratio.

    Lemme spend some time with my "charts" and I'll see if I can give you some meaningful feedback.
     
  3. zakk

    zakk 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    tires size was just there for comparison of who has to spin what.

    All crawl ratio's already have the x2 effect of the torque converter factored in.
     
  4. ZonkRat

    ZonkRat 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    88 SWB.right now 44-1,just fine around home,but,I want doubler for the mountains.If I find 465 would be 73-1,but,no OD.Mabey go to 42s.All I can do right now is wish. /forums/images/graemlins/grin.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/truck.gifer on 38s in TENN. /forums/images/graemlins/thumb.gif
     
  5. Greg72

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

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    Re: 700R/208: Poor Man\'s doubler?

    Zakk,

    OK I took all your numbers and plugged them into a table I already created for such an occasion. Here are a few obvious (and maybe not so obvious comments):


    #1 Rod's Setup:

    Deepest Axle Gears available = 5:13
    Deepest 1st Gear available in a slushbox = 3.06
    Deepest Xfer case gears (barring the NP241/243) = 2.61

    As a "non-doubled" setup, that's hard to beat....crawl ratio = 81.94

    The only thing that could improve the ratio is the NP241/243 case which has a ratio of 2.72:1 Rod could use that and get to 85.4:1 but it hardly seems worthwhile.


    #2 - Chris' Setup:

    Deepest 1st Gear available in a slushbox = 3.06
    Deepest Xfer case gears (barring the NP241/243)= 2.61
    Not so good axle gears = 3.73

    Crawl Ratio = 59.58:1

    The only difference between Rod's and Chris' setups are the DEEP axle gears, which you can see will add about 20 points of crawl ratio.


    #3 Zakk's Setup

    By now there are a couple of obvious points:

    1. The TH350 is losing ground to the 700R4 in 1st Gear (2.52 vs. 3.08)
    2. The NP203 is losing ground against the NP208 in LO range (2.01 vs. 2.61)
    3. Deeper Axle gears will help a little. Crawl Ratio will go from 41.53:1 to 51.97......but I suppose that's in the "who cares" category, especially if your spending $1000!!!

    Honestly, the math looks more sensible to apply that $1000 towards a doubler and leave your 4.10s alone.....crawl ratio = 82.04:1

    Or (God Forbid!) you could always swap out the TH350 for an SM465 and be at 108.45:1 with no additional changes.....



    So maybe 5:13s aren't the whole story for you Zakk???!!!
    /forums/images/graemlins/laugh.gif
     
  6. 70~K5

    70~K5 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    Just to throw one more thing in here. They make a 2.73 low gear for the TH350 too. /forums/images/graemlins/thumb.gif
     
  7. zakk

    zakk 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    For all my mulling over these options, I never even considered keeping my current setup and just adding a doubler /forums/images/graemlins/crazy.gif

    If I am able to procure a 205 for pretty cheap (32 spline version) then what do you think my overall expense would be? (guess-tamite?)
     
  8. Greg72

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

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    Re: 700R/208: Poor Man\'s doubler?

    Well if you help me find a job......it's FREE!!!!!

    /forums/images/graemlins/thumb.gif
     
  9. marv_springer

    marv_springer 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    Zakk,

    Reasons to do the doubler: /forums/images/graemlins/deal.gif

    1) flexibility of 2:1 or 4:1 will do better in crawling and wheel speed applications (sand) than the 2.72 or 2.6 low.

    2) beef, baby... the 208 or 241 can't hold a candle to it!

    3) later you could add a 3:1 in the 205 (hopefully), and be waaayyyy low.

    Marv
     
  10. 70~K5

    70~K5 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    WMS can do a 3:1 in the 203 range box right now. No having to wait for the magical 3:1 gears for the 205. Zakk there's 2 posiblities for you. You could do the WMS 3:1 in the 203, And later add the doubler and 205. Then you'd have 3:1/ 1.96:1/ and 5.88:1. More choises just in the TC's. Are you getting /forums/images/graemlins/confused.gif yet?
     
  11. bigmack

    bigmack 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    Damn go figure, I never thought of it like this. My set up is the worst of all, TH350/NP205/4.10's.
     
  12. Greg72

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

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    Re: 700R/208: Poor Man\'s doubler?

    Mack,

    You and me both.....
     
  13. zakk

    zakk 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    very true. I still think I would like some lower gears in the diffs. it feels like my little 350 is barely able to turn those meats. add some Hummer beadlocks and then I'm screwed! /forums/images/graemlins/eek.gif
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: 700R/208: Poor Man\'s doubler?

    </font><blockquote><font class="small">In reply to:</font><hr />
    Or (God Forbid!) you could always swap out the TH350 for an SM465 and be at 108.45:1 with no additional changes.....

    [/ QUOTE ]

    Pardon??? 6.55 x 2.01 x 4.10 = 53.97:1

    Personally I'd go with 4.56's and the Wagoner 3:1 gears for the 203 if I were zakk. The 4.56's will help driving around town and give it some more oomph. The 3:1 gears in the 203 will give it much better crawl. Swap a 700R-4 into a truck??? kidding right? I though you wanted to make it better? Swap a 208 in place of a 203? Also kidding I hope /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif Holy slip yoke batman...

    Anyways, with the 3:1's and 4.56's and the mystical 2:1 slip under the stall speed the crawl would be 68.9:1 and it would get out of it's own way for regular driving. 5:13's are cool, but do you really want to be turning 3150 rpm on the freeway just to do 65 mph?

    Rene
     
  15. Greg72

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

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    Re: 700R/208: Poor Man\'s doubler?

    Ooops! I guess I can't use the "Torque Converter 2:1" factor when substituting the SM465 into my Slushbox Tables!!!! /forums/images/graemlins/eek.gif


    BTW - Is the 465 a 6.55 or 6.58 ratio for first gear?
     
  16. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: 700R/208: Poor Man\'s doubler?

    It's 6.55:1, maybe 6.54. Those are the ratio's for first and reverse but I can never keep it straight. /forums/images/graemlins/crazy.gif

    Might be kinda cool to add a torque convertor to the front of a SM465....

    Rene
     
  17. zakk

    zakk 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    i do 2700 RPM's now for 70, so its not that big of a trade off.

    I was talking with greg and Dr. Watson suggests a 1 in. per RPM for crawling. I'll get the formula from Greg tomorrow if i can.

    I think I'll shoot for a 5.13 with a doubler. The doubler is running me $2,000 so that is waaaaaay off. 5.13's might be a stop gap measure.

    *edit* Rene, also remember that Dr. Watson runs a 700R so they can be made to survive.
     
  18. dammit32

    dammit32 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    I tryed to figure out my crawl ratio with:

    700r4/np241/4.10 14bff

    and came up with

    3.06/2.72/4.10 = crawl ratio 34.13:1

    Did I do it right?
     
  19. Shaggy

    Shaggy 3/4 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    </font><blockquote><font class="small">In reply to:</font><hr />
    Dr. Watson suggests a 1 in. per RPM for crawling

    [/ QUOTE ]

    <font color="green"> OK, let me try to wrap my head around that... So 1 inch per RPM? So if you idle the truck in gear at 800 RPM for 1 minute then you want the truck to have moved 800 inches, do I grasp that correctly?

    My setup is 465/205/5.13s = 66.53:1 crawl ratio.
    Circumference of a 42" tire = 131 inches

    800 RPM at the engine for 1 minute through a 66.53:1 crawl ratio would spin the tires around 12 times so the truck would travel 1575 inches in 1 minute. WOW! I really need a doubler apparantly. With a doubler it would travel 787 inches. Hmmm, interesting how the doubler gets me right to where the guy that sells it says I should be! (Just kidding Steve, I know that you speak the truth /forums/images/graemlins/wink.gif) If I add the 3:1 kit to the 203 then it goes down to 525 inches. That sounds pretty cool, but I think I'll just go wheel the piss out of the thing first though. /forums/images/graemlins/rolleyes.gif /forums/images/graemlins/thumb.gif

    Dammit, you did it right, but for an auto tranny you can add in another 2:1 of reduction to account for torque convertor slippage, so you'd be at 68.26:1.</font color>
     
  20. DesertDueler

    DesertDueler 1/2 ton status

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    Re: 700R/208: Poor Man\'s doubler?

    I am happy with my " poors mans doubler". I run a GM certa 700r4. They work great. I have had on in my truck for 20,000 miles now and no peoblems, and 15,000 miles was with 3.42s and 35" MTRs. Oh yea and I towed with that setup for most of those miles /forums/images/graemlins/grin.gif As for my NP208 its still good, but it only has 70,000 miles on it. I have yet to break a t-case, but broke a bunch of rear axles.

    Dan /forums/images/graemlins/burb.gif
     

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