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Diff Gear Ratio Question. 

 

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Posted: Fri Feb 23, 2007 8:24 pm 
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Or you could work out the diamater of the tyre quite easily.
You would just need to know rim size, tyre width and profile.

I wrote a program a few years ago that calculated revs versus speed. There are enough of them on the internet now I believe though.

 

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Posted: Fri Feb 23, 2007 9:13 pm 
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voxace wrote:
Or you could work out the diamater of the tyre quite easily.
You would just need to know rim size, tyre width and profile.

I wrote a program a few years ago that calculated revs versus speed. There are enough of them on the internet now I believe though.


There is a problem with that, different manufacturers, different tyres.
The one I remember from a while ago was a G'year Grand Rally S in 195/75R14 was wider and a little taller than a Dunlop Arrow 195/75R14.
I know these tyres don't exist anymore, but like I said, it was a while ago.
As long as all measurements are accurate, and the tacho is accurate too, it does work.

 

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Posted: Fri Feb 23, 2007 9:17 pm 
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Well while your at it why don't you measure the amount of turns at the axle as compared to the engine.
How do you know the manufacturer is stating the gear and diff ratios correctly?

I'm sure it's all close enough lol.

 

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Posted: Fri Feb 23, 2007 9:44 pm 
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voxace wrote:
Well while your at it why don't you measure the amount of turns at the axle as compared to the engine.
How do you know the manufacturer is stating the gear and diff ratios correctly?

I'm sure it's all close enough lol.


Because I've seen enough diffs to know that is the ratio they say it is.

 

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Posted: Fri Feb 23, 2007 10:08 pm 
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im going to go 3.5's or 3.9's, don't know which one yet, i don't want my car revving high all the time, but yet i wouldn't mind the extra go of the 3.9's, i think i got a 3.23 LSD or whatever comes factory in them....im not good with diffs, i only know engines, lol

 

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Posted: Fri Feb 23, 2007 10:16 pm 
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Storm wrote:
im going to go 3.5's or 3.9's, don't know which one yet, i don't want my car revving high all the time, but yet i wouldn't mind the extra go of the 3.9's, i think i got a 3.23 LSD or whatever comes factory in them....im not good with diffs, i only know engines, lol


If its an EB XR8, it would have 3.27's usually.

 

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Posted: Sat Feb 24, 2007 12:11 am 
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nah it's a Ghia

 

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Posted: Sat Feb 24, 2007 5:16 am 
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My EL Ghia has 3.45's doesn't it?
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Posted: Sat Feb 24, 2007 11:40 am 
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their was a sticker on the back / under side of my diff to let me know what it was exactly without guessing

 

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Posted: Sat Feb 24, 2007 1:05 pm 
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One Drone wrote:
I didn't feel a whole lot of difference. Go to 3.7s.


I agree - I have ED V8 - 3.7 LSD is big improvement.

Richie.

 

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Posted: Sat Feb 24, 2007 5:39 pm 
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Got 3.7 LSD in mine, huge difference over 3.23 single spinner that came factory... accelerates better, but is sitting on 2300rpm at 100km/h as opposed to the 1800 or so it use to do...

 

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Posted: Sat Feb 24, 2007 6:33 pm 
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Cobra - what did you do about speedo sender gear for the 3.7?

Richie

 

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Posted: Mon Feb 26, 2007 12:57 pm 
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1 have 3.91 in my eb 5.0l auto and i would recomend it. 2350rpm's at 100km/h and now its gone from 14.7l/100km to 16.5l/100km driving bout equal mix highway and city driving
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Posted: Wed Feb 28, 2007 12:59 pm 
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Would going to an XR diff ratio (3.45) take atleast .2 tenths of a second off you 4oom run, if so is there any benefit to going to 3.9:1.
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Posted: Wed Feb 28, 2007 1:10 pm 
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i would say it depends on if you have a stock or modded engine
i have basically stock but big exhaust and extrators so i would have lost a little bottm end and gain top end so the diff helped bottom end heaps as now its got the power to actually spin my new 235 18's
my old 1/4 time was 16.1 @91 so top end was pretty fast for that slow time so my take off was very slow but now i can feel its so much quicker but haven't had the chance to test it yet but it kept up with a BA xr6t which was supprising
but if i could guess i would say very low 15sec quater...so about 1 whole second quicker
i will post up my next run when it happens
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