The Definitive AU Diff Topic

[Eleanor]

In searching for info about AU diff swaps, upgrades, ratio and centre (LSD) changes I think I've searched and read every possible relevant topic here at AFF but I still don't have all the info. I couldn't find any info about this in the technical stickys above in AU.Falcon.com either.

I thought I would start this in the AU section so that those who have done diff swaps can tell others exactly what works.

Please don't reply here if your sister's boyfriend's mate's brother remembered hearing something about this from some bloke at the footy a few weeks ago and you're not sure if it's right, etc . I would hope that this becomes the definitive topic on what works and what doesn't!

Hopefully a moderator can work with me on this topic to delete any incorrect info that is added and compile a good list of what is known to work.

[Eleanor]

What I have learned so far.... (And please correct me if any of this is wrong)

28 spline axles were the only axles across all AU models.

The spread of ratios are 3.08, 3.23, 3.45, 3.73, 3.89 and 4.11.
I haven’t been able to determine exactly which ratios came out in which AU’s, with ute, wagon, sedan, XR’s all being different. Similarly I haven’t been able to determine which specific models LSD’s came in, and which are interchangeable.

Some vehicles being leaf sprung, some live axle coil, and some IRS means that complete diff swaps between models are not always possible.

Some AU live axle sedans have smaller diff housings/3rds that will only take 3.08 Ford gears. VL Commodore 6cyl R & P’s have a 3.45 ratio that will fit this AU diff.

Slotting in a 3.45 LSD diff housing from and EL into an AU won’t work easily as the EL diff is 70mm shorter disc to disc than the AU.

That’s about where I’m at at this point in time. If you have info you know is correct and has worked please post it up.

[GS608]

Forte/Futura
Manual 6 - 3.23
Auto 6 - 3.08
Wagon - 3.23
Auto V8 - 3.23

Fairmont
Auto 6 - 3.23 (LSD Option)
Auto VCT - 3.45
Auto V8 - 3.23

XR
All XR's - 3.45 LSD

[KR1STO]

Fairlane/ltd

Vct6 - 3.45:1 Non Lsd
V8 3.23:1 Lsd Opt

[GS608]

Ute
XL 1t suspension Manual I6/V8 - 3.45 HD
XL 1t suspension Auto I6/V8 - 3.23 HD

XL 3/4t suspension Manual/Auto I6 - 3.23
XL 3/4t suspension Manual V8 - 3.45 HD
XL 3/4t Auto V8 - 3.23

XLS sports suspension Manual I6/Auto I6/Auto V8 - 3.23
XLS Sports suspension Manual V8 - 3.45

XR sports suspension - 3.45 LSD

[KR1STO]

its amazing the variations between models and diffs hey..!!

[Eleanor]

Good info so far but I'm disappointed already! Looks like I have the smaller 3.08 ratio and housing in my Futura . I'm looking to go to a 3.45 LSD so I've got a bit of work to do.

[Dave_Obsession]

Originally Posted by Eleanor

Some AU live axle sedans have smaller diff housings/3rds that will only take 3.08 Ford gears. VL Commodore 6cyl R & P’s have a 3.45 ratio that will fit this AU diff.

This is interesting. Any idea how much it would cost to transplant a rebuilt VL 3.45 into an AU?? Has anybody investigated this?? I too suffer from the smaller 3.08 housing that won't take any other AU diffs :(

Does R&P stand for rack & pinion???

[Cadge]

Hey guys

Ive put a manual gear box and xr6 engine into a 1999 SI Fairmont. Should i look at putting the LSD diff in as well? What sort of gain would i get if i did?

[Eleanor]

R & P = Ring (crownwheel) and pinion.

It was in a topic that I found here (AFF) when I was searching for info and the poster was adamant that the Commy VL 3.45 R&P bolted straight onto the 3.08 centre. Only thing not mentioned was compatibilty of pinion bearings etc.

[Eleanor]

From this thread from 5 years ago:

http://www.fordforums.com.au/showthread.php?t=8577

Originally Posted by jonbays

Yes just to get it right in the AU fairmonts all 6's and V8's got 3.23:1 diff ratios.

AU Fairmont Ghias with VCT I6 got 3.45 diff with no option for LSD ( traction control fitted)

AU fairmont Ghia V8's 3.23 diff as above

LSD was an option on all non IRS models in AUI but dropped in AUII/AUII when traction control became standard across the range not just in the Ghia.

Originally Posted by jonbays

No AU Fairmonts came with LSD as a standard feature.

AUI Fairmonts except Ghia's or models with IRS option had the option for LSD.

AUII/AUIII Fairmonts the option for LSD was dropped.

I agree that traction control is the most likely reason as in AUII on traction control became standard across all Fairmonts not just the Ghia.

Here is the AUI brochure on the forum.

http://www.fordforums.com.au/photos...&cat=728&page=1

I can post up the AUII spec brochure if you want to compare them.

So it sounds feasible for 3.08 small-diffed AU2/3's, at least, that a LSD optioned 3.23 AU1 live-axle diff could be swapped in and the Ring & Pinion changed to one of the other ratios.

[Casper]

Originally Posted by XR-CHIEF

Forte/Futura
Manual 6 - 3.23
Auto 6 - 3.08
Wagon - 3.23
Auto V8 - 3.23

Fairmont
Auto 6 - 3.23 (LSD Option)
Auto VCT - 3.45
Auto V8 - 3.23

XR
All XR's - 3.45 LSD

Originally Posted by KR1STO

Fairlane/ltd

Vct6 - 3.45:1 Non Lsd
V8 3.23:1 Lsd Opt

Bit of confusion with the XR's in these 2 quotes.
Simple answer is all XR's had a 3.45 diff
All XR8 and XR6VCT's had LSD for the life of the AU's
XR6HP's had LSD as standard in Series 1 AU's. At some time in the Series 2 model life Ford cut costs and the HP's went from LSD standard to LSD optional.

[KR1STO]

where's the confusion Casper..? i didn't post about the XR's...?

[Jimmyd]

Minor error here re Ghia and LSD options as explored about month ago;

AU Ghia diff thread

Originally Posted by Jimmyd

Gee, I wonder what this little factory fitted item is then....








99 AU1 update Fairmont Ghia VCT with Tickford options


NB AU1 Tickford Suspension (basically the XR6 VCT package) was packaged with the 17" Alloy Wheel Option...


Memory was correct, listed as Not Available for IRS in the brochure...
Here

But listed as option with Sport Suspension in the AU2...
Here

And 3.45 was std ratio in the Fairmont Ghia VCT
Here



Cheers

James

This is a 99 AU1 Update Fairmont Ghia

Originally Posted by Jimmyd

AU Traction Control program works on difference in rotational speed for front wheels vs rear wheels - LSD would not be a factor in this calculation. The argument that Traaction Control & LSD don't mix was marketing hype at the time as to why the XR series did not get Traction Control - and no, I'm not making it up; I ran a Ford service dept in '98 when released and later moved in to selling them in 2001 while recovering from illness.

As per the post above the LSD is listed as packaged with Tickford Sports Suspension option in the IRS Fairmont Ghia Here ......

Cheers

James

[Dave_Obsession]

Thread-mine time.....this has been bugging me for some time, so I asked the guys at Etheridge Ford about AU diffs...

Originally Posted by Eleanor

Some AU live axle sedans have smaller diff housings/3rds that will only take 3.08 Ford gears.

I got the following response this morning from the service manager:

Originally Posted by Etheridge Ford

The part number for the diff housing is ER4010A- for series 1,2 and 3
So they are all the same as per parts microcat, so all gear sets should fit.

So does this mean that any AU 3.45 diff will fit, regardless of whether the donor car was IRS or live axle - since it's only the diff centre that's being changed, it's all good? Or am I missing something here - is there anything else that would be changed over???

[xr6_boss]

Hey guys i have an au xr6 II ute with a manual transmission and the diff is bout ******.. I also have a ute of the exact same model.. Only thing it has an auto. Wondering if i can swap them over and if ratios are same ??

[FGII-XR6]

I know in BA taxis they use either an AU , E series or commodore center to make them stronger (4 pinion to replace 2 pinion hemi) they are apparently the same and interchangable, made in the same factory

Originally Posted by xr6_boss

Hey guys i have an au xr6 II ute with a manual transmission and the diff is bout ******.. I also have a ute of the exact same model.. Only thing it has an auto. Wondering if i can swap them over and if ratios are same ??

yes you can swap them check the tag on the diff housing for the ratio

[FS5]

its been a while ,but my old girl runs 3.89 gear's out of some nissan rear end.its all about your diff and what will fit fit.from memory au's run a 78 borg warner diff and most commo's and nissan gears bolt straight in .both off irs and live axle diffs.if you want 4.11 i think they need to machine something.i remember starting a thread like this years ago or someone else did .??????

[Ford Falcon XR6]

Hi everyone just wondering what company does aftermarket LSD's for au falcon's ?? I had my Xr6 HP Au3 sold to me with the salesmen telling me it has an LSD which i later found out it doesn't (No lsd tag on diff) or at least it doesn't work. I though it's a little silly buying a whole diff when all i need is the centure anyone know who does them ? Hope it's still mostly on topic

Cheers Lorenz

[Antwon]

Yeah XR6 HP's dont come with LSD, only VCT models do. Im in the same boat, looking at getting a kaaz 2 way LSD

[Beer Baron]

Originally Posted by 5.0

Forte/Futura
Manual 6 - 3.23
Auto 6 - 3.08
Wagon - 3.23
Auto V8 - 3.23

Fairmont
Auto 6 - 3.23 (LSD Option)
Auto VCT - 3.45
Auto V8 - 3.23

XR
All XR's - 3.45 LSD

This still anoys me a bit because what series it is has an effect on diff ratio. There is a difference rolling diameter between the tyres so the diff ratio must change other wise ford is changing ratios in the gearboxes which i very highly doubt.

S1 forte is 3.08
S2/S3 forte is 3.23, No 3.08 in series 2 or 3

Correct ?

AU 1 XR6 HP had an LSD but it was an option on S2 and S3.

[The Monty]

Originally Posted by Antwon

Yeah XR6 HP's dont come with LSD, only VCT models do. Im in the same boat, looking at getting a kaaz 2 way LSD

HP's had it as an option, like the Baron has said.

[Dave_Obsession]

OK thread mine time...

I've now gotten my hands on a 3.45 LSD from an S1 XR6 to upgrade from my 3.08 single spinner. Have also gotten a speedo cog to suit as well.

From what I've been reading, the ECU uses speed, not RPM to determine gear shifts - so the easiest way to alleviate this is to transplant an XR6 ECU into my car. Alternatively, a J3 chip can do this for me using my stock ECU.

However, if I get the diff put in WITHOUT changing the ECU straight away, will this cause me issues - obviously there will be higher RPM's before gears change, but in daily driving conditions, will this be a massive issue?

I'm guessing at WOT this could be problematic...so the intent is to most likely go the J3 route, as that can be dyno tuned as well...

Is there anything else I should be considering?

[Whoosha]

Drop Chris or Theo at Blupower a PM Dave, they should be able to help Northern Diffs next door is Chris's old man

[blueoval]

Hey Dave,

I have fitted an XR6 diff and speedo cog to my car. I didn't need to change anything on my ecu when I got mine done. This was all before the s/c and any tuning. Drove it fine as it is. Still using the stock ecu as well. The Ecu is a learning computer as you know anyway, so it will get used to your driving style and cater for any changes. I normally drive around without the econ button on anyway. Seems to hold revs higher before changing anyway.

Not sure if that helps or not.

[The Monty]

I ran 3.9's with mine, and nothing was different?

[Dave_Obsession]

Originally Posted by Whoosha

Drop Chris or Theo at Blupower a PM Dave, they should be able to help Northern Diffs next door is Chris's old man

Last time I sent them both PM's about something else, I didn't even get the courtesy of a reply...

Originally Posted by The Monty

I ran 3.9's with mine, and nothing was different?

Originally Posted by blueoval

I have fitted an XR6 diff and speedo cog to my car. I didn't need to change anything on my ecu when I got mine done. This was all before the s/c and any tuning. Drove it fine as it is. Still using the stock ecu as well. The Ecu is a learning computer as you know anyway, so it will get used to your driving style and cater for any changes.

Thanks guys, this puts my mind at ease somewhat...if the ECU is going to relearn stuff anyway, then that's great.....I may well end up getting a J3 down the track anyway, for $200 a customised tune sent to me, and this can be further refined on a dyno...

Originally Posted by blueoval

I normally drive around without the econ button on anyway. Seems to hold revs higher before changing anyway.

'Power' mode does hold revs longing before changing....designed for towing or when 'economy' mode is just too slow I usually drive in power mode as I find a minimal difference with regards to fuel economy when not being crazy. I also find the transmission also kicks down more readily and this helps with things like overtaking etc.

[Day-mow]

Put a manual in and no issues XD

[TheSneakiness]

I went from a 3.23 single spinner to a 3.45 LSD in my AU ute and only replaced the speedo cog in the auto, no problems

[5.8]

I read somewhere that a LSD in an XR6 VCT became an optional extra in AU3's. Can anyone verify this?