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Discussion Starter · #1 ·
I have an Evo IV.
The problem is that a strange loud sound is coming from the rear only while cornering. The sound resembles that of a wheel touching the arch. We are thinking that the problem is in the rear diff.
I am from Malta and there are only three Evos here, all bought second-hand from Japan.
We have no manuals or workshop manuals at the moment, although they have been already ordered. And the Mitsubishi agent here knows nothing about them.
I would like to know what oil goes in the rear diff. (the oil you top from the luggage boot)and what is the procedure to change it.
Has anyone encountered the same problem and what is your opinion acout it?
I am desperate, please help me.

Discussion Starter · #2 ·
Sounds like classic problems with the AYC from what you say, i dont know too much about the problem as i have and E6, basically the problem affects the E4's and E5's, a bug the the AYC ECU. This topic has been discussed many times here, just do a topic search for it....


Discussion Starter · #3 ·
The oil in the boot reservoir is for the AYC,
U must use genuine Mitsubishi AYC oil. The changing procedure requires an electronic device known as a MUT11 , it can't be done correctly any other way and don't let anyone else try to tell u otherwise.
If the AYC level was low u wud see the AYC warning light on the dash.

Discussion Starter · #4 ·
Before you start to panic to much !!!!!
I had a simular noise some time ago.
It turned out to be the mud flap mount catching the wheel on cornering.
The mud flaps are so low that they easily catch the curb when reversing and bend the mounts.

The resultant sound was extremely disconcerting, very loud and I thought that something major
was about to fall of / fail !!!!


Discussion Starter · #5 ·
First of all thanks to all who replied.

Do you think that by changing the oil the strange sound will go?

Discussion Starter · #6 ·
If it is a transmission type problem then almost certainly not , the AYC fluid is used for on a hydraulic control system not as lubricant.
This type of problem is difficult if not impossible to diagnose at a distance , really it needs knowledgable first hand examination.

Discussion Starter · #7 ·
The AYC light on the dashboard does not stay lit.
is there anyone who has encountered the same problem? If yes, how did he solve it?

Can anyone send me an e-mail([email protected]) or fax(|PLS|356 465720) with all the exact procedures, if possible even diagrams, on how to change the oil and even what to do with the MUT11?
I've heard that you need some special tools to bleed the system. What are these tools and how do you use them?
From where can I buy the 'Mitsubishi AYC oil' from the UK?

I will be very grateful if you help me.
Thank you very much.

Discussion Starter · #8 ·

Glad to see you found the Forum, I'm sure that you will find it useful.

The tester we spoke about is called a MUT tester and most Mitsubishi dealers will have one. What you do need is the ROM pack for an Evo - this might be the hard bit for you in Malta! The Mut tester is used to help in the process of bleeding the AYC unit and we have not found a successful way of bleeding the AYC without it.

The noise that you are hearing does sound like the AYC unit and most of the faults with AYC occur when the fluid has not been changed frequently enough rather than an ECU problem. The Evo 4 was the first to have AYC and 5's and 6's suffer less from the problem.

Evoboy is right and as I said the other day the repair is not easy without the tools and someone knowlegeable. We do keep the fluid if your local dealer has the tester but I have to say that we normally have to replace the AYC unit to make the noise go away.

One solution could be to ditch the AYC and fit a conventional LSD unit in its place. I think that we have these available as well and although its cheaper than an AYC unit, its not good news on the price front!

Sorry to be the bearer of bad news buyt if you need any more ideas, you know where to find me

[email protected]

Discussion Starter · #9 ·
The oil in the reservoir in the boot is NOT the AYC fluid. This is the ATF dexronII fluid that is used in the hydraulic system
which actuates the AYC. The AYC fluid can only be checked for level by removing the appropriate filler plug in the diff.

The AYC diff has 3 oils associated with it and each has its separate compartments. The diff oil lubes the pinion and ring gears
and needs to be a 75W-90 synthetic gear oil. The AYC fluid bathes the clutches in the torque transfer mechanism, this needs to be the genuine Mitsubishi AYC fluid, nothing else will do. Finally, there is the hydraulic fluid , which is automatic transmission fluid ,
dexronII, which is used in the hydraulic system that actuates the transfer of torque between the rear wheels.

Unfortunatley, some of the 4's and early 5's had problems with both the AYC ECU and the clutch pack design that made them fail
prematurely, but some 4's were OK.

Check your chassis number against the recall numbers to find out whether or not your diff is affected ( -see thresds on recall)
If your diff is making a noise, make sure the AYC fluid is refreshed.
If noise persists try disconnecting AYC fusible link, the AYC light will come on but the AYC action will be disabled,
the diff should behave as a normal lsd and further accelerated wear should be reduced. See also threads on Coordsport forum.

I have serviced my own diff on my E6 and it has now covered 45k miles and is still quiet ( for now! ), changing the AYC
fluid every 10k miles. Mitsubishi recommend changing every 4500 miles because of the problems with the early 4's and 5's
but this does not cure the problem.
The workshop manual for the e5 states this fluid need only be change every 40,000km ( 24,000 miles).

What I have found by experience is that, changing this fluid every 10k miles, the fluid is darkened slightly and very
few particles have collected on the magnetic trap on the drain plug.
This will probably not be the case for a 4 or 5 that has the AYC ECU or clutch-pak problem.

If all else fails, look to use the RS diff (none AYC) or an aftermarket equivalent since a new AYC diff can be of the order of

-Good Luck

Discussion Starter · #10 ·
Wise words indeed. If your AYC is found to be faulty (hope not!) and requires replacement then I think the LSD would be a better option given your lack of dealer knowledge in Malta. The only point I would like to make is that the AYC will act as an Open type diff with the Fuse Link disconnected as far as know (i.e. no torque transfer will occur).

Discussion Starter · #11 ·
next question

is it possible to remove the AYC and replace it with RS Diff and do not get electonic problems
and how about the evo 7 with AYC in combination ACD

in the evo 7 it is all linked into one ecu ACD AYC ABS can you disable AYC ABS and a bunch of sensors in steeringwheel and wheel without get electronic failures



Discussion Starter · #12 ·
In principle yes as the AYC uses a seperate ECU. The AYC ECU has dedicated to it 2 G sensors, a steering wheel position sensor and a brake light sensor. The wheel speed sensors are also used for information but they are shared with the ABS ECU. The throttle position sensor is also used by the AYC but again that is shared with the main ECU.

Ditch the AYC ECU, the dedicated sensors and the hydraulric system and it should, in theroy, work OK (works alright on the RS)

Discussion Starter · #13 ·
Thanks to all of you guys for your help, especially Mr Mime.
I disconnected the AYC fuse (next to the battery), at first the AYC light on the dash went of but as I started driving the light came on. To my delight I found that the noise went off completely even in fast cornerings.

I would like to know if any damage to the diff. occurs while the AYC is disconnected.
Hence does anyone know what the sound might exactly be and what must be done.

In the meantime I would like to know what are the fluids that go in the diff. exactly called and what is the amount needed of each.

I'd like to thank you all agin, you have really helped me to figure out what might be wrong. Before I found this ite I was completely lost and had no idea.
This site is MAGIC!!!!!

Discussion Starter · #14 ·
Excuse my brain fade , the Mime is correct , the boot tank is ATF-SP11 , capacity 1 ltr ,

other oil s and quantities :-

Diff , GL5 spec 75w85 or 75w90 hypoid gear
oil , 0.41 ltr

Torque transfer mechanism , Genuine Mits AYC fluid-ONLY- , qty 0.70 ltr.

Co-ord Sort cud supply u with AYC fluid , the other fluids shud be available on Malta.

Discussion Starter · #15 ·
It does sound like you have contaminated AYC fluid or certainly trouble in that system. Particles in the AYC fluid will get stuck between the AYC clutch plates giving a grinding noise on cornering. The best bet is to replace the AYC fluid however as has been said above you need the MUTII to activate the valves which in turn allow bleeding of air fully from the system.
The fact that you have a grinding noise in the first place could mean you have a faulty AYC ECU which means the clutches are not operating correctly allowing wear of the AYC clutch plates. Wear of the clutch plates means particles build up in the AYC fluid and will get stuck between the clutch plates giving the grinding noise. The trouble is it ends up in a catch 22 situation because the more particles that build up the more the clutches will wear! This is the reason why changing the AYC fluid every 4500 miles is important as it will remove any particles before they do damage if your ECU is faulty.
With a properly working AYC ECU the fluid in theroy only needs changing every 24000 miles but the 4500 mile change over period hung on with the E6 as it was uncertain exactly what the problem was with the ECU!
(The above is information I have gained over the past year from various sources and is only my opinion of the problem and may not represent the actual problem fully.)

Discussion Starter · #16 ·
Thanks again guys but I still need to know if i do any damage by driving with the AYC disconnected.


Discussion Starter · #17 ·
Probably not , the fuse is there to prevent damage to the AYC system in the event of a fault , so if the fuse blew it wud be to isolate the AYC system from operating therefore being unable to cause further damage or potential safety problems for the driver.
It won't know the difference between blowing and removal

Discussion Starter · #18 ·
Evoboy is right.
Removing the fuselink disables the power feed to the hydraulric system. The actuators, pumps etc. will not work and your AYC diff will act like a standard open diff with no torque transfer occuring. Note that power is still fed to the AYC ECU even when the fuselink is taken out as the ECU is fed from a different location. This means that the AYC light may show a warning indication but it is nothing to worry about.

Discussion Starter · #20 ·
The part about the disconnected AYC becoming a normal lsd I had regurgitated from an answer from Cooordsport
on this very problem [Peter Collinson]. Hopefully, this would have come from a technical source either at Ralliart or Mitsubishi.
HH6 could well be right in that it would behave as an open diff ( loadsa rear wheel spin border|EQU| 0 align|EQU| absmiddle > ) rather than a normal lsd.
In either case, your clutch pak wear should have been reduced since the forced operation of the clutch pak [AYC torque transfer action] has been eliminated by removing the AYC fuse.
Evoboy, brain fade is my middle name. Luckily I had the manuals to hand, this time, to answer the question.

Mr Mime
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