# ORD doubler crawl ratio question

Discussion in 'The Garage' started by unick, Dec 19, 2003.

1. ### unick1/2 ton status

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What would the crawl ratio be for a truck with an 87 700R4, ORD doubler, and 4.56 gears be?

lmk
Nick

2. ### big83chevy4x43/4 ton status

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3.06 * 1.96 * 2 * 4.56= 54.698112 /forums/images/graemlins/thumb.gif

3. ### mechted1 ton statusPremium Member

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3.06 x 3.96 x 4.56 = 55.25

4. ### zakk1/2 ton status

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add in the torque converter for 110:1

I'm shooting for 153:1 /forums/images/graemlins/grin.gif

5. ### cybrfire1 ton statusVendorGMOTM Winner

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Zakk, how does the torque converter work in to the formula? Are you just multiplying by two? Is it different for different torque convertors? Thanks.

6. ### Greg72"Might As Well..."Staff MemberSuper Moderator

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[ QUOTE ]
Zakk, how does the torque converter work in to the formula? Are you just multiplying by two? Is it different for different torque convertors? Thanks.

[/ QUOTE ]

The "stall" in the converter allows you to spin the engine without a direct 1:1 coupling to the tranny...the effect is estimated at about a 2:1 ratio (conservative) to maybe 3:1 (optimistic).....

Once you hit the stall speed of the converter, the effect is gone. But for most of the slow speed stuff we do, this extra 2:1 reduction is REAL and welcomed! /forums/images/graemlins/thumb.gif

7. ### sled_dog1 ton status

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so in theory would puting a higher stall converter(not much say 1500) create a more optimal state? Cause you would still have the torque mutliplication?

8. ### Greg72"Might As Well..."Staff MemberSuper Moderator

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[ QUOTE ]
so in theory would puting a higher stall converter(not much say 1500) create a more optimal state? Cause you would still have the torque mutliplication?

[/ QUOTE ]

From everything I've read, and seen on this site.....changing the stall speed is more likely to make things worse than better.

Stall is a pretty tough thing to mess with from a "tuning" perspective. It's a PITA to get to the converter, and most of what I've heard indicates that you really need to understand what you're doing or you may just make your setup more unpleasant....

I forget what factory "stall" is, but I thought it was up in the 2000+ RPM range anyway???? /forums/images/graemlins/thinking.gif

9. ### cybrfire1 ton statusVendorGMOTM Winner

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Thanks for the info. Makes sense I just never really thought about it that way.

10. ### bigjbear1 ton statusStaff MemberModerator

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[ QUOTE ]
3.06 x 3.96 x 4.56 = 55.25

[/ QUOTE ]
Close, but it's x2 not +2, big83 got it right. The farther away from 2:1 get the more wrong you will be. Klune-V "Goliath" &amp; an NP241 (2.7:1 &amp; 2.72:1) 102.48:1 vs 75.63:1 or Klune-V "David" &amp; an Atlas (4:1 &amp; 4.3:1) 240:1 vs 115.81:1.

11. ### 88K5Jimmy1/2 ton status

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What do each of the number stand for in the formula? First gear ratio, low t-case ratio, a constant and gear ratio?

Thanks
Ross

12. ### bigjbear1 ton statusStaff MemberModerator

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Trans 1st x range box x x-fer case low x R&amp;P
700R4 x NP203 range box x NP205 x his R&amp;P ratio
3.06:1 x 2:1 x 1.96:1 x 4.56

In the example #s I used his 700R4 and R&amp;P ratio to get the finial drive ratios listed.

13. ### ntsqd1/2 ton status

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[ QUOTE ]
[ QUOTE ]
Zakk, how does the torque converter work in to the formula? Are you just multiplying by two? Is it different for different torque convertors? Thanks.

[/ QUOTE ]

The "stall" in the converter allows you to spin the engine without a direct 1:1 coupling to the tranny...the effect is estimated at about a 2:1 ratio (conservative) to maybe 3:1 (optimistic).....

Once you hit the stall speed of the converter, the effect is gone. But for most of the slow speed stuff we do, this extra 2:1 reduction is REAL and welcomed! /forums/images/graemlins/thumb.gif

[/ QUOTE ]

Somewhere in my Granddad's FSM or literature on his GMC motohome it states that the torque multiplication factor of the stock converter is 2.6:1 and cautions that only X p/n converter be used in the GMC coaches as the typical TH400 converter's factor is ~2.0-2.3:1 depending on application. Unfortunately he's already checked, that converter no longer exists in any inventory anywhere in the states.

14. ### fourwheelerjeff1/2 ton statusStaff MemberModerator

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this is what i am shooting for:
3.06 x 3:1 (wms) x 1.96 x 5.13 = 92.3 /forums/images/graemlins/eek.gif

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