Just replaced the rear bearings and hubs on the AU3 XR8 independant rear suspension.
The Ford workshop manual advises to discard and replace the Pac Nuts.

The original nuts have been used twice so thought I would take the manuals advice and replace them.

Rang Bayford spares and they advised that the pac nuts are now obsolete and they do not carry them.
Rang around Repco and such and no joy.

On eBay they list Front pac nuts but they advise that fronts are different to rears.

Would prefer not to use the nuts a third time....

Anyone had any solution or suppliers of these nuts ??

BA/F Packnuts are the same.

Thanks, I'll check that out tomorrow.

OK, I think I have my answers:-

1. The PacNuts front and back are the same physical size, however, their innards are different.
The innards of the front PacNut has 4 plates where each is the same thickness.
The innards of the rear PacNut has 4 plates as well but 2 are thick and account for 2/3 of the space in the cage and the other two are thin and occupy about 1/3 of the space inside.

2. The threads on front and rear axles are 24mm x 2.0mm.

3. They are definitely a single use item.
In subsequent uses their holding capacity is severely reduced (this according to the developer of the nuts).
Not a dangerous issue on the rears ... it would result in stuffed bearings and hubs and a lot of noise if they became loose.
On the front, however, one could loose the front left wheel.

4. The Ford workshop manual tools section nominates a 35mm socket.
I measured my nuts (yes, I know how that sounds!) before I had a copy of the manual and I measured 35.5mm so I bought a 36mm socket. A 35mm socket would be a tight fit but my 36mm works just as well as it is a single hex. If one was to use a double hex socket then I would suggest that a 35mm one would be best.
Given the torque spec (325nm rear and 305nm front) I would suggest an impact socket would be preferred and they are all single hex.
It could be that a tight fitting socket (i.e. the 35mm) may be a requirement for correct operation of the nut ... I am uncertain of that at this time.
If you were going out to buy a socket then the 35mm would be the one to get.

5. The rear nuts are still available as part number ER 1138 F ($38.76 each incl GST)... the guy at Bayford was wrong.
Bought some today from another Ford dealer.

6. On eBay one can buy front PacNuts for around $10 to $15... there are lots of sellers of these hence the competitive pricing.
One of the sellers I contacted advised that they would be listing the rear nuts soon and at $65 each !
If some of the other guys decide to sell these then competition will drive the price down.
In the meantime, get them from Ford.
The fronts from eBay were absolutely identical to the rears from Ford (other than the innards).

7. There appears to be only one supplier of PacNuts. OEM Fastening Systems.
I have requested more info from them, just for my own edification.
The two thicker plates in the rear nuts would allow for higher tightening torque, but, one would want a stronger resistance to loosening on the front.
The manual states that the rear torque spec is 325nm +/- 25nm (300 to 350 range)
I would like to understand why the different nuts were specified between front and rear as the torques front and rear are so close (i.e. why not be able to use front nuts on the rears)?.
Only thought, at the moment, is hardness of the axles where the fronts may be a harder steel than the rears hence a wider plate in the nut is required for the rears and that the narrower plates in the front nuts could damage the thread on the rear stubs ??.

8. PacNuts must not be tightened with a rattle gun.

I have requested info from OEM Fasteners on the versions of the 22x2.0 and am hoping that will shed some light on the AUs use of different versions.

Hi,
Firstly thanks for the info above. It's proven to be very useful.
After a recent rear wheel bearing failure (AU3 with IRS), I'm looking to replace the pacnut (as I believe the previous reuse of the pacnut was the cause for this failure!).
I'm having issues trying to source a replacement pacnut and I can't seem to find anything on the part number noted previously. I was wondering if the AU rear pacnuts are indeed the same as the BA ones? The front ones appear to be the same, but not sure about the rear??

I had issues with mine coming loose, even after fitting new ones. I have since taken to using loctite on used nuts and havent had them come loose since

I replaced my rear bearings (again) about 12 months ago.
Did not get new nuts but used Permtex Permanent (Red) thread locker (same as Loctite).
I slathered the stuff on where the thread is located on the shaft.
Checked them a month later, 6 months ago and again yesterday.
Have not budged.... torque of 325nm each time.

BTW, in the US they used castellated nuts on some of their cars.
They are listed per model and no info on thread size was available when I tried to check.
They are probably imperial sizes but always meant to get some just to see.
Would be better with a castellated nut and split pins.

Thanks all,
They certainly don't have the most thought through design! I'd much prefer to see a castellated nut arrangement (simple and effective).

Also looks like I should be prepared to replace the rear bearings on a regular basis!

Anyway, it looks like I'll proceed with the thread locker option. Might also investigate putting a lock nut on.

For anyone looking at this thread in the future, I can confirm that the front pac nuts are the same as the BA ones, but the rear are different to the rear BA ones. Unfortunately, it's looking like the AU IRS rear pac nuts are no longer available from Ford and I haven't yet been able to find any aftermarket versions.