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Old 10-23-2003, 01:20   #1 (permalink)
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Suitable diff ratio suggestions

Gday guys,

What diff ratio would you recommend to fit to an xf that runs a std auto and efi 6 mill with minor engine mods and exhaust/headers in order to get quicker off the line? I believe it currently has a 2.77 ratio with LSD.
I was thinkin of fitting a 3.25 ratio so it wouldnt impact a whole deal on the cruisability of the car that runs a speed auto box. Any suggestions? Are there other issues I should factor in when making a decision?

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Old 10-23-2003, 01:27   #2 (permalink)
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Re: Suitable diff ratio suggestions

If you dont do any highway driving or care about the revs your doing get 3.9 or 4.11 gears.

If you do a bit of highway driving i would suggest 3.45 or 3.7 gears.

This should help a fair bit with takeoff
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Old 10-23-2003, 03:10   #3 (permalink)
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Re: Suitable diff ratio suggestions

I have 3.9:1, i still get 28mpg on the highway.
And a nice punch off the line. 4.11 is to low
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Old 10-23-2003, 12:35   #4 (permalink)
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Re: Suitable diff ratio suggestions

Dont go to low with the new diff ratio

The ea before the one I have now. I put a lower diff ratio in it. went from 2.9:2 standard
up to 3.0:8
Made a fairly good improvment but remember if you have a manual you'll be changing gears more often so you might lose time there.
i went from getting 100k's out of second to only getting 85k's
So just bare it in mind.
Sure go super low if you have a race car but if you have to use it as a daily driver I wouldnt go too far with it.
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Old 10-23-2003, 15:06   #5 (permalink)
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Re: Suitable diff ratio suggestions

Don't go lower than 3.23. The 4.1 doesn't like to rev, and makes good torque. We recently changed an XF manual from 3.5 to 3.08 and it went better.
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Old 10-23-2003, 16:23   #6 (permalink)
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Re: Suitable diff ratio suggestions

What are the diff ratios that are avalible? Standard an non standard. I know the standard ones are 2.77, 2.92, 3.08, 3.23, 3.27, 3.45, 3.7, 3.9 and 4.11. Ive heard of 3.5 as a non standard are there others?

Im looking at changing my diff ratio from 3.27 (V8 manual) but I think going to a 3.45 would be a bit pointless since its a mall change and 3.7 would be a bit short for the highway.
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Old 10-23-2003, 19:52   #7 (permalink)
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Re: Suitable diff ratio suggestions

ED XR8 = 3.27. EL XR8 = 3.45. Obviously Ford thought the small change was worthwhile. Although mathematically small, you will notice the improvement going from 3.27 to 3.45.
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Old 10-23-2003, 21:38   #8 (permalink)
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Re: Suitable diff ratio suggestions

NZ, the 3.55 came out in the older Fords, like the XT 6cyl.
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Old 10-24-2003, 00:29   #9 (permalink)
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Re: Suitable diff ratio suggestions

I wouldn't go lower than 3.25 as you have no overdrive and the old 4.1 isn't much of a revver.

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Old 10-24-2003, 01:01   #10 (permalink)
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Re: Suitable diff ratio suggestions

Kerry, whats wrong with 4.11 gears? If he doesnt care about revving on the highway.
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