The ayc filler plug is at the rear of the diff housing and high up. Its is obscured by the crossmembers, but is stamped ' OIL '.
Jack up the rear of the car, crawl under and look forwards to the diff, joggle your sight around over the crossmembers to the diff housing u should see it.
Removing it is easy, but replacing it takes a lot of patience because of limited access, but it can be done. Check your hands for fit BEFORE u remove it. You will need a 17mm ring spanner for the
filler plug and a 24mm socket for the drain. Remember the normal diff oil plugs are nearby , dont get them mixed up.
To fill it u need a large syringe and some tubing, or get some empty mastic tubes and make your own large syringe ( I believe RS Components now sell these ).
I have changed my AYC fluid on my e6 5 times now and have had no problems.
Good luck !
I echo what sixmad said about the respective fluids. I believe the ATF in the boot is Dexron-II
as used in automatic boxes, but the AYC fluid is a special Mitsubishi recipe and cannot be substituted by anything else.
The AYC Fluid and the ATF used in the hydraulics ( boot ) reservoir are different oils.
The hydraulic atf is normal dexron-II( probably III now as u say) stuff used in autoboxes. The AYC fluid although red definitley has a yellowish tinge compared with normal ATF. Now it maybe that the additional additives in the AYC fluid play very little role in the life of the diff clutch pack , but on the other hand ..................
Ralliart and any dealer worth his salt will only use the genuine Mitsubishi AYC fluid, available from Coordsport, to replace the AYC fluid in the diff.
The AYC fluid is probably only a mix of ATF and diff oil or some combo like that, but it works !
If you are using normal atf in the clutch compartment of the diff u wanna monitor the wear carefully,
just in case.
As DJACK says Mitsubishi recommend that the ayc is done every 4,500 miles. This frequent changing stems from problems with early AYC diffs. The e6 AYC diffs are much better. The e5 technical manual stated it need only be done every 40,000km or 24,000 miles.
I have replaced mine at 10,000 mile intervals and have found very few particles on the magnetic trap and the fluid to be darkened only slightly.
The diff has now covered 62,000 miles and is still quiet and works well.
Its useful to know that SP-III can be used in place of the original item. Did u get that info from Coordsport/Ralliart ? And did they also let u know that the original AYC fluid is to become obsolete ?