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Discussion Starter · #1 ·
Hi All

Following some discussions a while back about a groaning diff and an apparently faulty AYC, I decided to rip out the hydraulic unit yesterday. HH6 mentioned that it could be a problem with the filter or hydraulic switch. I have stripped the hydraulic unit right down but I cannot find a filter anywhere! Where is it? Has anybody else stripped down the unit yet? There is no real help in the technical or sevice manuals which leads me to think that this is a sealed unit - may god strike you down if you dare take it apart .

Everything seems to be in very good order (apart from the external corrosion) so I am wondering if the unit is not faulty afterall. The motor runs sweet and pumps well and the valves seem to work without hesitation and with a nice definate click . I intend to rig it up on the bench and try and get some measurements of pressure etc.

Any thoughts anybody?


Discussion Starter · #2 ·
According to the system diagram in the E4/5 Tech Information Manual (page 2-18) there is a filter between the check valve and relief valve, I have no idea how accessible it is but this being blocked I would have thought would possibly give the symptoms you were getting (pressure not building up quick enough after initial AYC activation?). It is certainly worth looking at, that's if you can get to it. It should be on the suction side (obviously!) after the pump but before the accumulator. I think you need to remove the pump and check inside the block it was attached to, it must be in there somewhere unless the manuals were lying of course!

It could also be a few other things such as:
Oil Leak (doubtful as you would have noticed the level drop)
Loose/defective harness or connector
Defective Accumulator Pressure Switch (Hydraulic Switch)
Faulty AYC ECU

I have just had a quick check through the E4/5 and E6 manuals and the E6 workshop manual does provide a bit more info on checking the Hydraulic unit (pressure output test, it should output 1.0-1.6 MPa). It also has a diagram on the removal and installation of the hydraulic unit which may help indentifying bits. Combine that with the E4 TIM pages 2-18 to 2-20 is the best I can come up with. I will email you the relevant pages from the E6 manual.

By the way were you getting any error code output?

Discussion Starter · #3 ·
Just got my E4 back. Had loads of low groaning noises with normal driving and some extra high pitched squeeling when under hard pressure. The diff unit was re-conditioned and now the car drives a lot better, feels more solid and the low noises have gone. I can still get a high pitched squeel though if I get the back breaking (worse round left corners). But I'm gona get the system bleeded again, hopefully it's just the oil/air causing this.

Sorry it's prob not helping you but thought it was worth a mention.

Discussion Starter · #4 ·
Hi Fordy,

Having had all your problems myself, I can tell you that the noise you hear when cornering is caused by one of the AYC plates which has sheared inside the diff. The Old E4 diffs are not upto the job I'm afraid. I fitted a 2nd hand E6 diff in my car and have never had any problems since :)

I tried recon'ing my old diff but you can't get the AYC plates......

Call Clive at RC Developments cos he may have some plates left over from AYC Cusco replacement he did a little while back.

Call on the phone..... they get loads of emails so response can be slow sometimes.


Discussion Starter · #5 ·
Ahh nuts :)

After fully examining the hydraulic unit this weekend and putting it back together (pictures to come when I have uploaded them) I realised that the fault is definately with the diff. The hydraulic unit is working perfectly. I thought I had it licked whilst driving down a nearby country lane until I really started throwing it side to side (a-la touring car driver trying to warm his slicks) when boom it went and the groaning came back worse than ever.

Upon looking very closely I can see signs that the diff has come apart at some point (gasket sealant at the top of the diff just poking it's head out. I think with all the problems people have had with the ECU and the Mitubishi experts telling me Oh, it's the Pump and amp;lt;kerching and amp;gt; I overlooked the obvious - my diff is on the verge of exploding. Good :)

I'm not sure which way I'll go now. It think it might just be better to fit an RS diff and be done with it.

Discussion Starter · #6 ·
Sad it hear that :(
You may indeed be better off to fit an RS diff, you can certainly sell the working AYC parts on to help towards the cost. Remember you not only need the RS diff but the RS driveshafts aswell as they are a different length. I am not sure if you need a different propshaft or not though (anyone know?).

Discussion Starter · #7 ·
Thanks for that Jonathan,

That's a good help, I'm going to get what I can out of the man who recon'd the diff. If it doesn't solve I'll look at E6 parts.

Wallet's starting to get nervous !!


Discussion Starter · #8 ·
You could probably throw a Cusco diff in the standard diff housing also, probably be cheaper than the RS diff aswell.

Discussion Starter · #9 ·
Yes, you do need a different length propshaft (s/[email protected] £350), as well as different Subframe (s/[email protected] £200) and longer length driveshafts, to house the £1,600 RS rear diff ( new, but CoOrd out of stock at the Mo!).
I have a spare 6 GSR AYC rear diff for sale for £850 instead, if thats any use to you.
All the best, RogerRally
PS: I also run a Cusco rear diff fitted in my GSR casing on my 4, cheapest solution!
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