diff ratios for ef xr8 - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

XRQTOR · 06-12-2003, 04:17

i have an ef xr8 if i change the diff ratio how much acceleration can i expect ot gain and what difference will the revs be like at 110k'ph

Hot Ef · 06-12-2003, 04:36

hey mate. ive got an ef fairmont, standard diff ratio, thinking of going up to the 3:45 gears. ive heard there is hardly any difference at about 100kph, (maybe 250-300rpm), so its not much.

depends how high ur going in ur diff ratio.
and yes, you will definitely notice the difference in take off power off the line, quite a bit seeing that the XR8 already has a higher ratio ne way.

b-juggles · 06-12-2003, 05:07

I have a v8 fairlane and I want to know the exact same thing! Mine currently has a 3.27 LSD...I was thinking 3.7 or 3.9 gears...it currently runs at about 1800 at 100...with 3.9s it would run at about 2200 ish at 100kph

(to work this out, find percentage increase in gearing, add 1, then times by your current revs at 100/110/whatever)

As for gain acceleration, no real way to work it out expect in real life...

So yeah, what do you all think......I would really like 4.11s but that would prob rev to hard on freeway...car is auto btw

Also, anyone got any good recommendations on places to go to get quotes/advice etc?

NZ · 06-12-2003, 05:56

The thing with the 4 speed auto is that the shift points are load dependent. Its going to hold the shifts a fair bit longer with a substantial change from stock. We recently fitted a 3.08 into an NC fairlaine (3.27 stock) and it had a small but noticible difference. It shifted later as there was more load on the trans.

EDIT but of course if your putting a shorter ratio in its going to shift sooner :)

XRQTOR · 06-12-2003, 05:59

YEA MINES A 5SP MANUAL AND IT GET REALY LOUD ABOVE 2500 REVS SO IT SHOULDNT BE TO BAD AS IT DOES 110 AT ABOUT 2K

NZ · 06-12-2003, 06:03

If its a 5 speed your away laughing! Not like your not the one choosing when to dhift like the slush box

XRQTOR · 06-12-2003, 06:06

so how much quicker will it be off the line with the new diff and wats price should i expect to pay for it

BLWNEB · 06-12-2003, 07:46

Bro manual go 3.7LSD.

YOOT · 06-12-2003, 16:34

I am dieing to get my hands on a 3.45 LSD to replace my 3.08 open diff, only thing is I can't find anywhere that will ge me one. the DIff lapping shops want $1500 for one, bloody stupid.

Help me! BRISBANE.

b-juggles · 06-12-2003, 18:19

Quote:

Originally posted by NZ
The thing with the 4 speed auto is that the shift points are load dependent. Its going to hold the shifts a fair bit longer with a substantial change from stock. We recently fitted a 3.08 into an NC fairlaine (3.27 stock) and it had a small but noticible difference. It shifted later as there was more load on the trans.

EDIT but of course if your putting a shorter ratio in its going to shift sooner :)

shifting sooner though is that a problem? wat does that mean? that car will still rev all the way out wont it?

It wont like always shift at say 4000 at WOT instead of 4700 will it? Meaning that you will have to place in first if you want it to hit 4700 rpm, then change up to second, then third and so on?