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I started thinking the other day about the effect that a lower ratio diff would have on my XF. At the moment it is 2.77 single wheeler and I would like to get a 3.23 or 3.9 :1.

Would the car go a crap load better with a 3.23 or would i be better with the 3.9??

The car is a 5spd so I would hope that when cruising at speeds its not yelling. Does anyone have any experiences with this ratio change or could someone point me in a direction where i could get some info?? One last question, what revs would the motor do at 120kmh in 5th with both the 3.23 and 3.9?

Cheers
Matt
 

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Territory TS - AWD
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Matt,

Some simple arithmetic says that with the 3.23 you revs will rise around 1.2 times and with a 3.9 they will rise around 1.4 times everthing else remaining unchanged.

So if you do say 2500rpm now at a given speed and gear you would be doing ~2900rpm with the 3.23 and ~3500rpm with the 3.9's.

I would suggest 3.23 for an everyday driver with minor engine mods. The 3.9 would be more suited to a very rev happy engine and short sprints (not happy on the highway).

Just my 2cents.
 

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From what a guy at work said with his XF, it's doing 2700 somethin at 100km/h. I got a 3.23 in my baby and she turns 1950rpm at 100km/h.

Oh yeah acceleration will be heaps toey with the 3.23, if you want a good compromise get the 3.45 (XR's have got em)stronger takeoff and at 100 you'll be doing 2200rpm.
 

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BSR Twin System (tm)
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I have a friend who replace his 3.45:1 gear set with a 4.11:1 unit. At 100 km/h on the highway I think he was doing around 2600 - 2700 rpm in fifth gear.
 

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EA S said:


My 2.92 with a T5 pulls 1900 at 100kmh in 5th. What transmission do you have?
I've got the BTR T5OD, which is an evolution of the T5, ratio's can vary from gear to gear. By the sounds of things it looks like i've got a taller 5th gear than yours which is offset by the shorter diff ratio.
 

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EF_Falcon_GuY said:


I've got the BTR T5OD, which is an evolution of the T5, ratio's can vary from gear to gear. By the sounds of things it looks like i've got a taller 5th gear than yours which is offset by the shorter diff ratio.
Sounds like yours is the one to have for highway driving with 3.23.
 

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EA S said:


Sounds like yours is the one to have for highway driving with 3.23.
Yeah she's quite relaxed at highway cruises, and really hauls from 110km/h onwards. A touch of the gas at 110km/h and it will see 140-150km/h.

But i would want it to be alittle nippier off the line to 80km/h. I think a 3.45 would do the trick.
 

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EF_Falcon_GuY said:


I think a 3.45 would do the trick.
I was going to go for 3.45 as there's not enough jump from 2.92 to 3.23 to justify it, but I've heard that 3.55 are more readily available and cheaper, but I haven't looked into it yet. Then again, the 2.92 moves pretty well once it winds up a bit and I've started to wonder whether I might leave it in and just put more punch into the donk. Decisions, decisions.
 

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Sideways..
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xf_xr6 said:
I started thinking the other day about the effect that a lower ratio diff would have on my XF. At the moment it is 2.77 single wheeler and I would like to get a 3.23 or 3.9 :1.

Would the car go a crap load better with a 3.23 or would i be better with the 3.9??

The car is a 5spd so I would hope that when cruising at speeds its not yelling. Does anyone have any experiences with this ratio change or could someone point me in a direction where i could get some info?? One last question, what revs would the motor do at 120kmh in 5th with both the 3.23 and 3.9?

Cheers
Matt
Mate, you are looking for exactly the same diff as me :) Ive been looking for sooooo long to find one in the papers... I cant seem to find one at all.

Ive rang up some places, they want about $450 or so, to make one up with 'custom' ratio of 3.23.

So if anyones got a LSD 3.23:1 diff for an xf.. in the Perth area, gimme a holler at [email protected] :)
 

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Hi XF Falcon,
have you checked the site www.quokka-onine.com ?

If you haven't checked it , just type diff in "search",can't be easier. Only problem is it shows all ads including complete cars if the word diff is mentioned. Best part is that it is local for us,sandgropers.
Best of luck with your diff.
Regards Jon (dragonV8)
 

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yeah thanks for that link.

I pretty much buy the quokka every thursday anyway. I'd say that 99% of the diffs that people are selling are the usual open wheel 2.77's or 2.92's. No one seems to be selling any LSD 3.23/3.9

Eventually one will turn up.
 

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Ok, so which diffs from other Falcons (either the whole diff, or just centre) would fit straight onto an '86 XF Falcon sedan?
 
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