
FordFairmont 


Posts: 6166 Joined: 8th May 2007 
Who here is running this combo?
Im getting 3.7 diff gears put in shortly and wanna know what revs its doing at 100km/h. Cheers!! 

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stef4001 



im running a ed with a ea t5 box in it.i nealy do on the rpm meter 1900 doing 100km.no diff change.got the standared one still in the car.i hope this helps.good fuel econemy
_________________ thanks guys 

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FordFairmont 


Posts: 6166 Joined: 8th May 2007 
Hmm.
Isnt there anyone who has this combo? Is it that bad? I know theres a formla to follow but im getting different figures from the diff specialist. The formula someone posted on FordMods gives me 2300rpm @100km/h and the diff bloke reckons 2450rpm's 

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jrfttf 



PM SENT!?


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cjh 



FordFairmont wrote: Hmm.
Isnt there anyone who has this combo? Is it that bad? I know theres a formla to follow but im getting different figures from the diff specialist. The formula someone posted on FordMods gives me 2300rpm @100km/h and the diff bloke reckons 2450rpm's Here's the formula to work it out.
_________________ http://youtu.be/jJTh9F3Vgg0 

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EggHead 



I guess you could use
Engine rpm at 100k's X New diff ratio / current diff ratio = New engine rpm at 100k's eg. 1900 X 3.7 / 3.23 = 2176 Should give you a rough guide. 

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FordFairmont 


Posts: 6166 Joined: 8th May 2007 
Yeah ive tried that formula and found 2300rpms @100km/h works out to be correct for 3.7's in my car.
But the diff bloke did i different, i told him my car does 2100rpm @100km/h with 3.23 diff, so he divided 2100 by 3.23, then multiplied by 3.73 and come up with 2400 or something like that. Which do ya reckon is more accurate? 

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cjh 



FordFairmont wrote: Yeah ive tried that formula and found 2300rpms @100km/h works out to be correct for 3.7's in my car.
But the diff bloke did i different, i told him my car does 2100rpm @100km/h with 3.23 diff, so he divided 2100 by 3.23, then multiplied by 3.73 and come up with 2400 or something like that. Which do ya reckon is more accurate? The formula ( that I posted ) is very, very accurate. The drag racing mobs use that formula.
_________________ http://youtu.be/jJTh9F3Vgg0 

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