The Definitive AU Diff Topic

[needaXYGT]

I noticed that 4.11 was mentioned in the second post! Does anyone know what model these were fitted to?

[Whoosha]

Originally Posted by dave93761

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

.

Yes I forgot you may need a B infront of the A

Originally Posted by needaXYGT

I noticed that 4.11 was mentioned in the second post! Does anyone know what model these were fitted to?

4.11s were never factory fitted in AUs even after market requires shimming .

[Dave_Obsession]

Originally Posted by Whoosha

Yes I forgot you may need a B infront of the A

Yes I have since learned that , but it's basic customer service to let a potential customer know if you can't help them...maybe even suggest somebody else who would be able to assist...

[zakjames]

So just wondering guys.
I have a series 2 XR8 ute auto beam axle, any idea what diff they come with standard and what ratios I could fit in?

I only ask because I didnt see any mention of the utes.
Cheers guys.

[Sox]

Originally Posted by zakjames

So just wondering guys.
I have a series 2 XR8 ute auto beam axle, any idea what diff they come with standard and what ratios I could fit in?

I only ask because I didnt see any mention of the utes.
Cheers guys.

It will be 3.45:1, and LS.

You should be able to slide in anything up to 4.1:1.

[Ride]

Just another one for the records. My AU II Fairmont Ghia also came with a 3:45 LSD, was a bit surprised when I got underneath it the other week when I was pulling the tailshaft off. I suspect the reason why it received one is due to the Tickford 17's and sports suspension + IRS that it received (options on the Tickford compliance plate).

[5.0 ED]

Something i'll point out that was originally mentioned about the 3.08 diff's, its actually not the casing that is different it is the centre itself, you can pull the actual centre out and replace it with a different say 3.45 centre and use the other diff gears.

Commodore 3.45 VL gears that fit are non turbo and 75 series, they are super weak and break very easily, i really dont recommend this path.

My diff in my ED is a 3.08 factory unit, i replaced the centre with a LSD unit out of a 3.45 XR6 EF from memory, and install 3.45, then 3.89 and then 3.91 diff gears into it.

The 3.45's broke, the 3.89's broke and wear always noisy, and the 3.91's are nice quiet and super strong. unlike the weaker made 3.45's and 3.89's. The key point here is, there are stronger made 3.45's in ford's and weak one's in commodore's except Turbo's and so on.

All v8 ghia's both fairlane and fairmont i have see have had 3.23 single spinners...

[BHDOGS]

I have an au 2 fairmont v8 live axle I assume I have the 3.08 diff as nothing's written on my diff housing and there's no LSD tag so this means I can rip the center out and just put any 3.45 LSD center in from another live axle 6 or 8 live axle au?

[Dave_Obsession]

Pretty sure that's right. As it's only the centre, I'm also fairly sure it doesn't necessarily have to be from a live axle AU.

Fairly sure if you stick a 3.45 centre into a 3.08 open diff, you'll end up with a 3.45 single spinner (ie not LSD).

FWIW, I asked my mechanic about this topic, he said it's a real pain to change a diff centre over, easier to get a replacement diff and they can install that....so that's what I did! Not installed yet but soon!

[5.0 ED]

AU 2 fairmont V8 live axle should be 3.23 LSD.

[BHDOGS]

Hmm really? It's got tickford suspension from factory if that makes a difference how can I check if there's no markings on diff?

[auIILTD]

Does anyone have any idea what this Diff is from? I am guessing as it does not have LSD on the tag, it is a single spinner. Does anyone know what the high performance tag means?



Stu

[ic0nic]

Hey guys, I'm exploring the possibility of throwing a LSD into my 02' AUIII. What would my options be here? I'm a little sketchy on the details that I need.

[blueoval]

Originally Posted by ic0nic

Hey guys, I'm exploring the possibility of throwing a LSD into my 02' AUIII. What would my options be here? I'm a little sketchy on the details that I need.

Try and source a complete diff assembly from an XR6 rather than muck around getting diff centers changed. That is what I did. All I did then was gave the new diff some fresh oil and it was all good.

[greenguzzler]

Originally Posted by 5.0 ED

Something i'll point out that was originally mentioned about the 3.08 diff's, its actually not the casing that is different it is the centre itself, you can pull the actual centre out and replace it with a different say 3.45 centre and use the other diff gears.

Commodore 3.45 VL gears that fit are non turbo and 75 series, they are super weak and break very easily, i really dont recommend this path.

My diff in my ED is a 3.08 factory unit, i replaced the centre with a LSD unit out of a 3.45 XR6 EF from memory, and install 3.45, then 3.89 and then 3.91 diff gears into it.

The 3.45's broke, the 3.89's broke and wear always noisy, and the 3.91's are nice quiet and super strong. unlike the weaker made 3.45's and 3.89's. The key point here is, there are stronger made 3.45's in ford's and weak one's in commodore's except Turbo's and so on.

All v8 ghia's both fairlane and fairmont i have see have had 3.23 single spinners...

I have an AU Fairlane V8 series 1 with 3.23 LSD and traction control. I am the second owner.

[Day-mow]

3.23 say i want to be sporty but i really just dont cut it.
you need minimum 3.45. a real man would put in 3.9's

[Cookie-XR8]

mine is getting 4.11's and a mini spool, all you will ever need.

[falconnut]

my car in sig is stock what would be the cheapest lsd diff i could get put in? Not really interested in higher ratio just the stock ratio in lsd

[BHDOGS]

a second hand one out of another falcon would be the easier and cheapest one to do.

[falconnut]

k thanks.

[zakjames]

Does anyone know what size the actually crown wheel is?
I keep seeing kits for 8" and 8.8" ford diffs ?

[auIILTD]

Sorry to drag an 'oldish' thread, but I note that both Dave_Obsession and Rapid Axe have both change the speedo gear when going to 3.45. Can either tell me the number of teeth and / or colour of the speed gear that goes with the 3.45?

Cheers
Stu

[ebgtjames]

23 teeth - Black, haven't we been through this in your build thread Stu?

[auIILTD]

Originally Posted by ebgtjames

23 teeth - Black, haven't we been through this in your build thread Stu?

Yes we have been through this James, but I have heard conflicting stories. I have not discounted your input, just seeking confirmation. Some of what I have heard may mean colours were changed? The afore mentioned guys have done this to an AU.

Do it once, do it right. Forums are a free source of info, cannot hurt to ask.

Stu

[ebgtjames]

Yea fair enough Stu might be different with the Au?

The EB GT Autos have 3.45s, 17x8.5 rims with 245/40/17 tyres from the Factory, the "Technicians Data Guide" that comes with them shows the Auto as having the 23 teeth Speedo Drive, this was confirmed when we took the Auto out and changed to Manual (black gear) and I re-used it in the T5, with Chad manning the Quarterhorse he confirmed my Speedo to be spot on ..

Yours will still be out with that gear as you've got a larger diameter rim/tyre combo

[auIILTD]

Cheers James. If I find any different, I will be sure to post it here for future reference. Still keen to hear Dave and Rapid Axes input.

Cheers and Merry Christmas.

Stu

[Dave_Obsession]

Still haven't done mine yet - the diff is sitting round the back of our house The diff and speedo cog I got were from an S1 XR6 HP...speedo cog is grey and has 22 teeth...hmmm maybe I was given the wrong one?

[auIILTD]

Originally Posted by Dave_Obsession

Still haven't done mine yet - the diff is sitting round the back of our house The diff and speedo cog I got were from an S1 XR6 HP...speedo cog is grey and has 22 teeth...hmmm maybe I was given the wrong one?

Thanks Dave. Grey and 22 teeth rings a bell as to the conflicting information that I have. I guess I just have to stop being lazy and get under my car and pull the 3.23 speedo gear out, count the teeth and get one with one more tooth.

Cheers
Stu

[EvilChief]

The good old BW 8-3/4" Differentials (solid axle only)

Any BW diff prior to EA had a different housing and center, but same same diff gears as newer BWs.

Housings between E-series Falcon, A-series Falcon, Commodore Vl - VS and R31 Skyline are different in terms of tube length, but housing is the same, hence any center carrier (open or LSD or spool) is the same right across the above mentioned models.

The axle splines are determined by the guts of the centers, regardless of Open, LSD or locker. VP, VR VS (possibly VN), R31 and most Falcons run 28spline axles.

The carries between Open and LSD are different and are not interchangeable, as the LSDs are "friction cone" based with a spring loaded center, where as the opens use spider gears with pins, however these are again identical across commodores falcons and skylines and are interchangeable. (Note to "tighten" LSD centers, shims under the center springs increase the cone pre-load, which retains the LSD in locked position and rises the break away friction load, to do it on the cheap regular washers can be used instead). (Please note there are aftermarket LSD options available that are not friction cone based, but come with their own carrier specific to their design).

When changing any component within a differential they must be re-shimmed. First off the pinion needs to be shimmed, in order for the pinion and crown to mesh on the full face of each other. If the pinion is not shimmed out correctly (not enough) then it will run on the toe of the crown and whine. If its shimmed too far out (too many) then it will run on the heal and once again whine. Either way it will lead to premature failure of the diff, by destroying the teeth on either the crown or pinion. It is imperative that they are shimmed so that the pinion contact surface is exactly in the middle of the crown contact area (use engineering blue to test). This may require several removals and re installations of all components to get right and is quite labor intensive.
Ensure to set preload on pinion when making up pinion nut (crushing the collapsible ring). There are tools available that will measure the preload based on the friction of bearings against their seating cones, or you can do it by feel. It should feel fairly firm with some effort to turn, but without nodging or hanging up.
Now the crown needs to be also shimmed in order to set the backlash. Determine the overall width off the original diff center including shims, bearings, cups etc, when fitted to housing, and compare that to the new overall width of the new center, if one is being fitted, if old center is reused, usually the shims are still correct, just mark right and left accordingly). To determine the backlash, use a dial gauge to determine the free play (rocking crown forwards and backwards and forwards with pinion stationary and observe gauge. Off the top of my head this should be between 7 to 11 thou. Adjust shims until this achieved.

A possibly usefull or useless fact, R31 manual Skylines ran 3.7 differential that will also fit falcons and commodore BWs and ran 28 spline axles centers. This is actually my most favorite diff ratio in all my Falcons, as they are common and cheap.

[ic0nic]

Hi guys, I'm hoping you can shed some light on my most recent purchase.

I found a 2000 AU XR6 at the local wreckers with a diff stickered as 3.45:1. The diff ratio change from 3.08 should be a noticeable improvement by itself, but would this particular diff also be LSD? I've looked over all of the bolts but I can't locate a tag as pictured in the earlier posts.

Merry Christmas everyone