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Grinding noise from rear when accelerating (with videos)

18899 Views 32 Replies 16 Participants Last post by  Bnick1995
Help!!! I have a 08 evo x with about 40k on the clock and its my daily driver and I drive her with care. Early this week it started making a grinding/donkey moaning noise from the rear (almost like its coming from the diff) and it only happens when accelerating in 1st, 2nd, 3rd and when cornering at speed with a shift of weight.. I took it to the dealer and the tech could get it to doit in normal driving but when put on the lift they couldnt. Now that I have been thinking and doing some research I am thinking its the AYC. i have seen alot of issues with them online including them being burned up and I would like to solve this issue ASAP. I have 2 seperate videos where I have recorded the noise while driving.. Thanks in advance Brandon

video 1

video 2
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I just dropped mine off at the Mitsu dealership for them to bleed the system for me. I suspect that it may have been inproperly serviced by the last dealership it was at. It was low on fluid when I got it so I hope it didnt suck up any air into the pump. I am going to try diconnecting the solenoids as well to see if I can narrow it down any farther.
Have you found anything out about this, I'm having the same issue. It started after the changed my clutch out and I found the AWC resavoir empty, I topped it off and I still get the noise! Air in the lines perhaps but how do you bleed them out?
Resurrecting an old thread as I got EXACTLY this today for the first time.

Checked fluid was below minimum with no warning lights, waited to cool down, fluid rose to minimum, checked floor, no oil leak, haven't checked under carriage as yet.
New member here, got an 2011 Evo X 2 weeks ago. Took it to Cobb and had them look everything over and got an Accessport aswell. Left there, got home with no issues. The next day I go to leave my place and this exact noise started to happen, basically just like the guy in video described. Has any one came up with a solution to this? sorry to keep this old thread alive.
So what's the deal with this. I have the same thing and so have others yet not one person who has had the issue and posted it in this thread have listed a solution. Did everyone just ignore it?
I would love to know, still happening to me several weeks later. I havent had a chance to take it and get it looked at.
I believe the acid/ayc needs to be bled. I'm having mine done tonight an I will update and let you know if it fixes it

Sent from App
Acd/ayc needed to be bled. No more noise.

Sent from App
Not sure if you've resolved your problem, I have the exact same noise, and by exact I mean identical.
I first walked in my dealership assuming it was my rear diff, turns out it was actually a heat shield around the fuel tank resonating at around 3k rpm. I admit the noise is very deceiving and seems like a huge issue, but try taking off the heat shield around the fuel tank, go for a test drive and I can assure you you won't hear the noise again. I ended up putting some thick double sided tape around the heat shield, haven't heard the noise since. Try it out and spread the word!
Throw-out bearing.The noise coming from clutch section,every-time u shift u can hear it grind.I dd my x i don't get that sound but mines a mr..
I'm just experiencing this with my 2008 GSR. Just had the AYC pump replaced under warranty.

It's definitely the AYC/ACD because when I pull the AYC relay the noise goes away.

Re-bleeding the system will be next.
Mitsubishi Dealer Came Through!

Hey guys, just checking it to share my recent experience with the AYC/ACD pump. I was having the exact same symptoms as the OP - same noise under the same conditions. First I called the local dealer to get a quote for bleeding the system (I figured even if it's a couple hundred bucks it's worth it to pay out of pocket for the fix). They gave me some ridiculously high price and they didn't seem to understand why the system would ever need to be bled based on what I told them. Keep in mind: at this point I hadn't brought the car in to the dealer yet, just talked to them on the phone.

I decided to take the car to the local performance shop to see what they thought, and they assured me it was the AYC/ACD pump but advised me to take the car in to the dealer since the pump should be covered under the extended warranty. Props to them for their honesty! I wasn't super optimistic about it, especially because my AWC fluid res was full and I had no codes/DTCs, but I scheduled an appointment at the dealer and brought it in.

The technician who called me agreed that the pump was making a strange noise, but explained that their policy required there to be a DTC to confirm the part was actually broken. He opened a case with their tech hotline and they said there wasn't enough evidence to warranty the fix. I was very patient but didn't budge on my stance that it was failing, and the tech contacted a Mitsubishi representative who finally authorized the fix under warranty!

Long story short, I was pleasantly surprised that Mitsu replaced the pump under warranty and I picked the car up with zero balance due. I can't guarantee everybody will be so lucky, but it's always worth a shot!
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New member here, got an 2009 ralliart. And yesterday I go to leave my place and this exact noise started to happen, exactly like the guy in video described. Has any one came up with a solution to this? Thanks for the help!! :)
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