AYC Diff

[Jimbo]

I don't remember reading anything about this in the past, so I thought I'd throw this open to see if anybody has any info or advice.

Ever since I bought this VR4 I've been getting intermittent problems with the AYC diff making low sounding grinding/droning/graunching noises. Within in a week of getting it I had both the AYC fluid and diff gear oils changed which seemed to cure the problem for a while, but in the past few months the noise has become ever present, but far, far worse on left handers than on right handers, and ONLY when the AYC lights are on.

The old car started making a higher pitched whine last Easter and I assumed that to be the brake discs. Sure enough, once I swapped the discs over to the new car, the same noise transferred over as well. Unfortuantely there's also this much lower grinding noise on the new car that was occurring before I swapped the discs over.

I've just come back from Mitsy who've done me a free oil change on the diff as they drained it and found it to be BLACK (this is after 5000 miles). Sadly it's still not solved the problem as I get the same horrible noise when doing sharp or long constant radius left turns with power applied (just enough to get one bar, so 15-20mph is enough!)

I'm convinced that there's something wrong with the diff itself, as the AYC pump appears to be working fine. To further this assumption (and to differentiate it from the possibility of it being the drilled grooves of the brakediscs rubbing against the pads, which is what I think the higher pitched noise is), when I drive in the snow at 5mph in straight line and stab the throttle, i.e. so you get all AYC bars lit up momentarily, the same horrible low pitched grinding noise appears.

Can anybody shed any light on this, or has anybody ever experienced anything remotely similar? I'm convinced my diff is knackered.

[BraindG]

Mine does this aswell, ive got a feeling its something to do with the ayc fluid.

I used to get this groan before i changed the AYC switch, which also involved changing the fluid. For quite some time the noise was gone, and only recently has it returned..

So i dont think its something like the diff itself. Could just be an airlock?

[Nick Mann]

Which fluid was black?

[Jimbo]

It was the diff's gear oil that was found to be black and that was drained and refilled today.

Last summer I got them to change both sets of gear oil, and also the AYC fluid, so I'm somewhat bemused that it could be "black" now.

[Jimbo]

What's the AYC fluid for? Is it just for lubricating the pump, or does it have a more active involvement in the diff itself?

It was last July I had the oils all changed, and then they would have redone the AYC fluid last Novemeber when it had it's 72000 service, and today they've drained and refilled the diff gear oils again.

So in theory I've had all the different sets of fluid changed TWICE by a Ralliart mechanic in the past 8 months and only 5000 miles.....I wonder whether it could be an airlock, Barry.....hmmm, but Mitsy are supposed to use a special kind of bleeding tool to ensure this doesn't happen

[BraindG]

im not sure tbh, all i know is I had the noise before changing my AYC switch, then it went away... now its back... all ive done in the meantime is change the diff oils..

[Nick Mann]

The only part of the AYC that can get an airlock AFAIK is the hydraulic side. But the oil that was black was the gear oil? Surely the gear oil is just that! The AYC fluid is for the hydraulic side and the clutch side. I would have thought those are the parts working harder under AYC cornering.

The black oil/airlock thing doesn't add up IMO.

[Jimbo]

Yeah I'm completely puzzled by it. I didn't see the oil myself, I just got the impression from reading the expressions on the Mitsy guys faces that the oil was looking decidedly tired, but "black" is the word they used. I must admit Nick, it does sound rather odd now you've mentioned it that they should use that word to describe a substance that's not exactly world famous for being bright or translucent!!!

Could it just be that the AYC fluid wasn't changed for a long time until I bought the car? I'm thinking maybe the clutches have been damaged in some way due to contaminated oils, and that any oil change now is too late.....does this make any sense?

[Nick Mann]

Black gear oil is worrying. I guess it depends on there definition of black. Most gear oil is a yellow-brown sort of colour when it is fresh. But what I meant was gear oil is gear oil. If the gears are turning (which they must be if the car is moving?) then the oil is working or it isn't.

My guess for the noise would be the hydraulic or the clutch fluid, but both are AYC fluid and therefore have nothing to do with your black gear oil. Maybe the gears work in different ways with the clutches engaged/disengaged so the problem is with that part of the diff? I guess we don't have enough experience between us.

Next bet would be to try Roger Rally I think. He impressed me with his knowledge of AYC - maybe he can confirm/deny options?

[Jimbo]

Yeah, good idea - I'll see if I can track him down on the MLR. I'm also going to return to Mitsy tomorrow to see what they can come up with - they seemed to be convinced that this oil change would solve the problem.

I'll post back I know more.

[BraindG]

Jimbo, out of interest, does your car judder a wee bit under acceleration?

[Roadrunner]

Pretty certain it's your AYC clutch-lubrication fluid. These are precisely the symptoms I'd expect if the fluid's knackered.

[Jimbo]

Jimbo, out of interest, does your car judder a wee bit under acceleration?

Nope, nothing like that. The car is sound save for this grinding noise that appears on left handers and in perfect sync with the AYC lights appearing....

....difficult to test this completely safely, but it appears to be a louder sound the more bars I get. When I was last on a dry track and pushing it (Snetterton) I was getting three bars and the noise actually started to sound sort of springy/clunky, if that makes any sense - I backed right off when I heard this and the noise hasn't come back since, but I've not been remotely close to 3 bars since either.

[Jimbo]

Pretty certain it's your AYC clutch-lubrication fluid. These are precisely the symptoms I'd expect if the fluid's knackered.

Yeah, that seems to be the consensus Brian.....but this fluid is documented as being changed twice in the 10 months and 5000 miles I've had the car. I say documented, because I'm now a little uncertain as to whether this was actually done....especially with the gear oil being reported as contaminated.

[Kieran]

Yeah, that seems to be the consensus Brian.....but this fluid is documented as being changed twice in the 10 months and 5000 miles I've had the car. ....

I wonder if they have just changed the AYC Hydraulic fluid and not the clutch pack fluid - it's the clutch pack fluid that gets contaminated...

[amsoil]

I'm a little troubled to hear about black oil coming out of a diff; I have heard of this but never seen it; it it was black then something is very very wrong there. If it was the auto fluid side its not too uncommon but still not good news; just make sure they put in Mitzy own ATF not Dextron 3 which doesn't make the grade and was designed for something else.

[Rally205]

Jimbo,

The noise is caused by small particles of dirt trapped between the clutch plates inside the diff. When the AYC kicks in it compresses the clutches and you get the noise. I had it on mine when I first bought it and I thought that the diff was knackered so I had it checked at Mitsy and they said it was knackered too. I bought a second hand diff and put that in.

The new diff did it too!! I had the fluids changed three times and it went away. I also found somemone to re-build my old diff. He stripped and checked it and said that there was nothing wrong with it. Bugger!

It can also be caused by using the wrong fluid ie Dexron III. This causes the clutches to slip and you get a horrible grinding noise. Just make sure that they use the right stuff and get it changed regularly.

[amsoil]

Jimbo,

The noise is caused by small particles of dirt trapped between the clutch plates inside the diff. When the AYC kicks in it compresses the clutches and you get the noise. I had it on mine when I first bought it and I thought that the diff was knackered so I had it checked at Mitsy and they said it was knackered too. I bought a second hand diff and put that in.

The new diff did it too!! I had the fluids changed three times and it went away. I also found somemone to re-build my old diff. He stripped and checked it and said that there was nothing wrong with it. Bugger!

It can also be caused by using the wrong fluid ie Dexron III. This causes the clutches to slip and you get a horrible grinding noise. Just make sure that they use the right stuff and get it changed regularly.

If you struggle to get Mitzy's own you can get the only oil thats to that spec from me as below; If you check the threads you will get the idea and there is a club discount in the members section which makes becoming a full member a good investment for those who aren't already. Also think Amsoil is cheaper than Mitzy's?

[Jimbo]

I had the fluids changed three times and it went away.

Excellent stuff Marcus, thankyou very much for that.

My AYC fluid has supposedly been changed twice, so from your experence, could this mean that it just hasn't been flushed properly? Did Mitsy do the same with yours - i.e. just drain and refill it the first couple of times and then only when you found the new diff made no difference did they do a monster flush and refill?

[Jimbo]

If you struggle to get Mitzy's own you can get the only oil thats to that spec from me as below; If you check the threads you will get the idea and there is a club discount in the members section which makes becoming a full member a good investment for those who aren't already. Also think Amsoil is cheaper than Mitzy's?

Hi Don - I received 10 ltrs of ATF from you on Tuesday (and at warp speed too, I might add ) all ready for my gearbox flush.

Isn't the AYC fluid a different type of oil altogether though?