Rear AYC Diff Replacement
This tutorial covers the basics for replacing the AYC rear diff on the entire Evo 4 to 9 range. The diff's are all physically the same in appearance, although the four is the weakest, and the 7diff onwards is the strongest. There is also another difference, as once i had fitted this Evo8 diff to my Evo 6, the car was certainly alot more tail happy, meaning i had to reset the rear geometry to factory setting (i.e. 3mm toe in) to calm things down.
Once the exhaust system has been removed, along with the prop shaft, you can drain the two oils and undo the hydraulic lines to the rear of the diff.
The lower suspension arms need to be removed from their inner fixings, this is a good opportunity to also clean up the adjusters as they will be inevitably be full of dirt. *In hind sight you may be able to get away with removing them at the other end without disturbing the geometry.
Also remove the rear anti-roll bar. Be warned that the drop links are very expensive, so use alot of releasing fluid, and instead of a spanner i would recommend mole grips to prevent the threaded studs from spinning. Alittle heat on the nuts wouldnt go a miss in hindsight. The drive shafts are easily released with a light tap of a hammer....
To release them fully from the diff you just need a firm tug of the whole hub/shaft assembly outwards to get enough movement.
Remove the three bolts at each side of the alloy diff carrier.
Remove one of the centre bolts, undo the other but leave it in place.
Place a trolley jack under the main diff housing and take the weight.
If you look past the alloy carrier in this picture you will see the cast steel carrier - this is held up by two large nuts on studs. Remove the two nuts and washers.
Lower the diff, alloy carrier, and steel carrier down together..
Evo 8 diff on the left, Evo 6 on the right ....
You will need to change over the cast steel brackets from the 6 diff onto the 8 diff i'm afraid as they are different.
Swap over the two carriers, re-tighten all the bolts and your ready to lift the new diff into place.
Once again use the jack to lift the diff up into position. Fasten in place and push the drive shafts in firmly so they seat correctly.
If you removed these bolts make sure you grease them well when you put them back in.
New diff with AYC hydraulic lines connected.
The shiny bolt head at the top is the AYC oil fill. It needs less than a litre of oil. Only ever use Mitsubishi ATF SP-III Diaqueen or an equivalent that is rated to Mitsubishi Diamond SP-III.
The normal diff gear oil (<1 lt. of 75w90) goes in the bolt hole top right of this pic. In both cases fill until oil starts to come out the hole, then screw the bolt in.
There you go, all back together again. You will need to have the AYC hydraulic system re-filled and bled at the first opportunity. Until you do pull the appropriate fuse to prevent the pump from running.
Oh, in case you wondered where the new diff came from.... ouch!