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Ratio change. Yes! ... But what to do with speedo and trans? 

 

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 Post subject: Ratio change. Yes! ... But what to do with speedo and trans?
Posted: Mon May 30, 2005 12:50 pm 
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Guys,

Can I have some light shed on this area, I have done a ring around here in Sydney and got conflicting stories ...

I figured that I would have to ensure that the trans ECU gets the correct speed signal as well as the speedo ... Is this true?

What do I need to do to ensure the 3.7's / 3.9's work in harmony with the rest of the ED V8 automatic?



Cheers,

 

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Posted: Mon May 30, 2005 2:17 pm 
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i am pressuming u have or want to change your diff ratio.

if u ring Ford and tell them what you have done u should be able to get a spedo gear to chaneg which will give the correct speed readings to the dash ecu etc

 

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Posted: Mon May 30, 2005 2:34 pm 
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Yeah and dont take any of their crap, Ive heard storys of people chasing them for months to find out that they 'do' stock them! and for about $15 for an auto

 

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Posted: Mon May 30, 2005 4:55 pm 
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Ford stock them ?????


Even for ratios that were not offered by them?

.... this is all that is need to keep all the ECU's working in harmony?


Cheers

 

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Posted: Tue May 31, 2005 1:36 am 
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5150 wrote:
Ford stock them ?????


Even for ratios that were not offered by them?

.... this is all that is need to keep all the ECU's working in harmony?


Cheers


yup they should do!

and yes all ya need :) piss easy! just ask for a spedo gear ( driven gear )

 

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Posted: Tue May 31, 2005 7:59 am 
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Well then? Anyone here know a helpful Ford dealer in their area who can assist? Or does anyone know what part numbers I should be asking for?


Cheers,

 

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Posted: Tue May 31, 2005 10:12 am 
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Just ring your local and tell em you need a speedo gear, if you dont know what ratio its 'was' just tell em your model and they'll work it it out, then tell em your new ration and they'll (hopefuly) get the right gear for ya

 

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Posted: Tue May 31, 2005 12:23 pm 
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i know the speedo gear effects the speed limiter but can anyone tell me if it effects the rev limiter? i wouldn't think that it would but i'm trying to work out why my ecu only lets me rev to 5200 while putting this same ecu in someone elses car it revs to 5500 before hitting limiter.
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Posted: Tue May 31, 2005 2:28 pm 
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on face value you I'd say no cause the revs are normally taken or your alternator, dont know about the newer cars but thats how its done on the old ones. When you change your gears in the diff you can expect different rpm readings than the same speed previous, thats just how it works. But the rev limiter..... well thats a tuff one! maybe someone with and ecu car can fill in that last link for ya

 

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Posted: Wed Jun 01, 2005 4:24 pm 
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no will not effect the rev limiter!
the difference in revs coudl be the gauges are out

MikGan wrote:
on face value you I'd say no cause the revs are normally taken or your alternator, dont know about the newer cars but thats how its done on the old ones. When you change your gears in the diff you can expect different rpm readings than the same speed previous, thats just how it works. But the rev limiter..... well thats a tuff one! maybe someone with and ecu car can fill in that last link for ya


umm NO the revs are not takes on the alt they are taken off the coil

 

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Posted: Wed Jun 01, 2005 7:28 pm 
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oops my bad

 

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 Post subject: Re: Ratio change. Yes! ... But what to do with speedo and tr
Posted: Sat Jun 04, 2005 12:48 am 
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5150 wrote:
Guys,

Can I have some light shed on this area, I have done a ring around here in Sydney and got conflicting stories ...

I figured that I would have to ensure that the trans ECU gets the correct speed signal as well as the speedo ... Is this true?

What do I need to do to ensure the 3.7's / 3.9's work in harmony with the rest of the ED V8 automatic?



Cheers,


You need to leave the original speedo drive in the trans, as the ECU is matched to the diff ratio the car came out with. If you change the speedo drive, then shift points and kickdown points, and also max allowable speed to manually downshift will all increase, in proportion to RPM

You will need to install a digital speedo adjuster just before the VSS wire reaches the instrument cluster to adjust the speedo. You can calibrate the speed adjuster on a dyno.

By keeping the original speedo drive, the ecu wont see any difference, therefore the shift points will remain the same in proportion to RPM, only that the vehicle will be travelling physically slower by 15-20% depending on your new diff ratio.
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Posted: Sat Jun 04, 2005 5:11 pm 
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http://www.fordmods.com/forums/documents.php?doc=30

thisi s a speedo calc but if u play around with it u can probably figure out what speedo gear u need
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