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What diff to shove between the legs???

6K views 45 replies 17 participants last post by  Trav 351 
#1 ·
I have a 3 Speed MPFI Ea Falcon, I will not be converting this to a 5 Speed Manual, but maybe putting a shift kit and shifter in etc... What diff would you recomend to pull harder and faster.

I still sorta want to go on freeways doin 100 or 110, but hardly ever do only on that one holiday occasion, what you recomend? and what does it do the the car sitting on high revs down the freeway???
 
#2 ·
Having a 3 speed, your options aren't too great. My car's a 4 speed with a 3.08 and when I had it in limp mode (stuck in third) even then it was starting to sh!t me up the wall at 100km/h. 3:27's will still be revin pretty high, but would be the ABSOLUTE max i'd go. Anything above that would just be stupid! (no offence to anyone who's done it :p)
 
#3 ·
knowing sfa about diffs all i can say is that the EF one is good for everything from cruising around to flogging ricers, well it does the job for me anyway, and it will take a shift kit. Im 98% sure mine is 3.45 but I could be wrong - whatever the standard EF Futura diff is, thats what ive got and it does the job fine.
 
#4 ·
The 3 speed doesn't really give you much to play with. From memory most of the 3 speeders had 2.77 to 3.08 (My EA 3 speed fairmont Ghia had 3.08). You could probably go to 3.23, 3.45's would be a bit steep I would think but you may get away with it.
 
#5 ·
I had a 3.23 behind a 3 speed. From memory it sat on about 2500-3000rpm at 100km/h. I know it topped out at a whopping 165km/h @ 4900rpm!! LOL.
 
#6 ·
What did the EB fairmonts come out with? It sits on 1800 RPM at 100kph, buggered if I can figure out the maths.
 
#7 ·
If you were thinking 5 spd, wait till after that.
I personally would get a manny over the 3spd anyday.
1st gear is way too tall, and coz it has 3 gears u get shitfull economy. (i had 1) Even put a 4spd in, as i think its not worth spending any mulla on modding the 3spd box.

The when u get the manny done, and still want more go, get 3.7s :)

My 2 c
 
#8 ·
My EBII Fairmont has a 3.27:1 Single Spinner, but they probably put a few different types in.
 
#10 ·
yhee jus put the 4-speed in
 
#11 ·
With a 3-speed you already revving pretty high at cruising speed - chuck in a manual and 3.45 then you'll be a shitload faster and still lower revs at 110 :angel:
 
#15 ·
look around for a xr6/8 diff as they came with 3.45 lsd stock. Thats probably the best compromise between performance and economy. I had it in my car till last week (pinion bearing collapsed, made a mess out of the crownweel) and they go hard and dont rev too high on highway.
Don't qoute me, but i've heard VLs came out with 3.45 and apparently the fit into E series. Dunno if they are lsd.
 
#16 ·
Or an EF/EL Fairmont or Ghia
 
#18 ·
doin up the 3speed auto is like doing up cfi i got a spare 4 speed auto lyin round make me an offer!!
 
#19 ·
If only converting from 3 to 4 speed was that easy. What I'm finding is that anyone interested in quarter mile performance would find that if they put in a good diff ratio, the car could hit its top speed well before the end of the track. :sb:

Interestingly, guys like Adrian Vella use a 3 speed C4 and run 10s with a 3.7 diff. Warrants some research I think...
 
#21 ·
well with 3.7:1 diff, and a C4 at 5500rpm with 28" drag slicks it would be doing 124mph. Which makes me think he revs it up to and pass 6000rpm.

6000rpm would be 135Mph. which is damn quick
 
#23 ·
Thanks for that Walky, sounds like a useful bit of programming. Come to think of it, the Adrian Vella EL does rev sky high which is a significant factor.

Axeman, rumour has it that 4 speed autos are now available for X series Falcons etc. Would be perfect if it has the strength of a C4. If I find out more I'll keep you posted.
 
#24 · (Edited)
That would be cool Jack.. I was talking to a fella in Repco the other day and he was astonished that X and early E series cars are not better catered for in the market place - just for the price of them and pure sheer volume that exist on the roads. Looking at my car today compared to the BA's in the Ford yard it almost seems as the styling is coming back around slightly.

*New info*

AOD 4spd auto with improved components looks nice. Probably no way to fit in E-series...

*End new info*

Dan...
 
#25 ·
Interesting thoughts for sure...

And another question for the experts among us, is it as simple as throwing in R31 Skyline diff gears into a 2.92-3.45 E series diff to get 3.7s, or am I confused? If so, it would cost next to nothing.
 
#26 ·
Here's something else equally interersting Jack....

[snip]
AP 108 Chev Auto (T350/T400/T700/Powerglide) to EA 6cyl 3.9/4.0 Ford
[/end snip]

Could anyone bear a TH700 instead of their 3spd BW?? Hmmmm....

Dan...
 
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