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AYC Fluid change (cure those donkey noises)

49152 Views 351 Replies 133 Participants Last post by  jhfozzy
Thought this may help some people who are having AYC sqwarking and grinding noses to try and cure it themselves.

This is a bit of a simple guide for people who are not familiar with the AYC clutch bath drain and fill procedure. Also I have covered the rear diff drain in this guide too.

I have just bought an Evo 5 with the classic sqwarking and grinding from the rear diff. It was quite a bad case and would even make a fair racket at slow speed turning. If you've got this problem then have a read.

Right, first off some tools you'll need..

17mm offset ring spanner
24mm socket (on wrench obviously)
oil drain tray (or container to catch oil)
refill bottle (old toilet duck bottle works a treat)
clear hose (to attatch to refilling bottle)

Also you'll need a litre (it takes less) of AYC fluid or Mitsubishi SP-III, if the car is making nasty noises I'd get a few lires of AYC fluid as you may well need to do more than one change to get it clean. I like to drain the AYC, refill with half a litre of new and drain again just to pull that dirt out.

If you're going to change the rear diff oil too you'll need a litre of regular gear oil 75w90.

Here we go then :naughty:

First, jack the car up at the back and secure on axle stands and chock wheels etc so it's nice and safe.

Get under the car and have a look at the rear diff area to get yourself familiar with the various drain and fill holes.

Here's what you'll see.

Note that the rear diff oil drain and fill IS NOT part of the AYC fluid system, it's regular gear oil.

Again another shot, note position of AYC fill plug.. it's at the back of the diff at the top and a bit fiddly to get to, not impossible though but just get your hand up there and work out how you're going to refit the plug when the time comes.

This pic was taken looking directly up at the diff.

I always like to remove the AYC fill plug before I do the drain (just incase) Please make sure you use a decent offset ring spanner (as picture) as they can be quite tight and risking destroying it with an open ended spanner is not worth it.

Once you've succesfully removed the fill plug then remove the AYC drain plug and the AYC clutch bath fluid will come out.

While I was under there I decided to put some fresh gear oil in the diff, this is not AYC related but the diff part, seperate fluid from AYC.. normal 75w90 gear oil.

You can see the refill hole

Once you've successfully drained the AYC fluid then you're ready to refill with new. I use a toilet duck bottle with a length of clear hose for this. You need to slip the hose into the fill hole at the top and squeeze away until the AYC fluid reaches the level of the fill hole (some will start to seep out the fill hole when full)

Here you can see my bottle :D

Once refilled then it's just a case of refitting fill plugs and you're good to go. As a matter of normal servicing of the AYC fluid you will only need to do a simple drain and refill


If you have noises from the rear diff I'd advise after draining to put the drain plug back and fill with half a litre of AYC fluid again then drain it again just to try and clean it out a bit more. Also if you do this and still have a slight noise after then I'd go for another change again in a week or so. From my experience it doesn't take much for the AYC clutch part to become noisey as far as dirty fluid goes! As you can see it's nice and simple, so no excuses.

Obviously the rear diff oil is a simple refill when drained and a lot easier to get to the refill hole.
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That's a good guide mate.
My diff has started making the same noises and i need to sort it before Llandow, i spent some time last night reading through your AYC threads.
I take it you have sorted the problem with your diff?
How many times did you have to flush the AYC bath?
How much fluid ATF fluid does the clutch bath hold?
Cheers :smthumbup
How noisey is yours? The car I've just done it on was very noisey! As I said even slow parking and turning it would grumble.

The car I did is about 95% better now. Only time it makes any noise (and it's a faint squeel) is on fast direction change off throttle. Flicking it left and right will provoke it into some noise but I'm going to give it another flush out soon. For example 10mph turns into a junction on this car would have caused a noise. The main thing is though it's a massive improvement so it gives me confidence I can completely rid it of any noise.

If your car is making pretty reasonable levels of noise I'm sure just a change would cure it.

I would (while you're under there) flush a bit through though.

I think it holds about 0.7L of fluid. Just fill until it starts to come out the fill hole. But if you're buying some then get a few litres while you're there IMO.
My diff isn't too noisy at the moment, i heard a whine last weekend when cornering fast on a very twisty road, sounded like i had a child in the boot that whimpered when i cornered really hard. I put the car away and haven't driven it since.
I asked how much it holds as i only have 1 ltr so not enough too flush and refill, but probably worth draining and putting clean fluid in for now?

By the sounds of it a simple drain and refill will sort that. Maybe (as you have it unused anyway) you could drop the drain plug and let it drain for a day or two, then refill.. should get it all cleaned out.
That's my day sorted then,
despite not being great with spanners i'm going to give it a go this afternoon (if you listen hard enough you may hear me swearing very loudly) :D
I will let you know how i get on.
Cheers Steve :smthumbup
Hi James! Sorry to be a pest but ive been told the ayc refill is the bottle in my boot! (EvoV) is that correct?
If you want to top up the pump section that is correct mate. On the right hand side of your boot is a removable flap, take it off and you will find a black container. That is your AYC fluid bottle.
Apart from topping it up, which i have never had to do, you shouldn't really need to touch it.
Ok, got tools out, jacked car up etc. Was all set then fell at the first hurdle, i can't undo the fill bolt :wallbang:.
As i can only get a spanner in there, i can't get enough leverage on it...................Bugger.
If you get a 'normal' spanner.. put the ring end on the fill bolt and then get another spanner (of similar size) and put the ring of that over the open end of the spanner you've got on the bolt (effectively making the spanner twice the length) and you should be able to undo it ok.
That makes sense, i will give that a go James.
How do you get the fill bolt back in after???? It looks like that will be the hardest part.
The 2 spanner method worked :smthumbup Now for the drain.
Job done :smthumbup
A great informative thread James, i never would of attempted it if you didn't supply the photo's. The fluid that came out was quite black and there was a fair bit of shite stuck to the magnetic drain plug. Took her for a quick spin and all seems well. Later on when the roads are quieter i will give her a blast round the twisty roads where i heard the noise last time.
We could use more threads like this.
Cheers Steve.
sorry to bring this back up again can i use: ams oil atf fluid
Yes mate, that's what i used in mine :smthumbup
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