Hey guys... So i'm not sure if this is drivetrain or suspension related. I've taken my car to mitsubishi a few times for this problem already and to no avail... Here's my story.

A little while back I started noticing a rotational tapping noise, it's most prominent and heard the loudest when the car is cold. But... it can still be heard after driving for a while. I say it's rotational because there is very exact timing and it increases or decreases frequency of the tapping with speed. After a certain speed, say 10-15 miles per hour, you can't hear it any more. I can hear it from the driver seat with everything off (radio, AC, windows up) and it can be heard from the back seat. As I've mentioned, I have taken the car to mitsubishi multiple times, the first couple of times they said the car was fine, finally after I couldn't take it because I knew it wasn't, they replaced the rear suspension, and of course, as I was driving away, the noise was still there. Apparently they checked the LSD, the wheel, axel, and everything. I've kept every single service write up and report. The sound is coming from the rear right part of the car. I've never had any accidents, the rims aren't cracked. I've only had routine maintenance done.

I finally bring this up on here because today, while I was driving on base, the noise went from a tapping to a strange sound. It was very brief but to me it sounded like a straining noise, kind of like how a pulley and belt sound when the belt gets caught or stuck. That's the best way to describe it, and to make it more difficult, I slowed the car almost to a stop and the intensity, loudness, and frequency of the sound didn't change at all. After a few seconds it went away though but it really freaked me out. I have no modifications to the car what-so-ever, I'm waiting until the warranty is up to do all that.

Does anyone have any ideas what it could be. I don't race, I don't drive the car hard or anything, I have my occasional spirited moments but nothing crazy. There are no check lights or warning, I'm pretty sure the tire pressure is normal, there are no nails in the tires, nothing is hanging lose in the wheel well, and all the lugs are tight on the wheel.

I was thinking maybe it was the LSD or something that has an electrical/mechanical relationship, but again no bells or whistles are going off in the car, but I do know people (early on) had problems with the pins snapping in the LSD. I'm supposed to take the car in Wednesday to get it checked out but I wanted to check on here as well to see if anyone has any insight.

Thanks a lot for any responses or feedback.

*Mods if you need to move this thread NP. Thanks*

 

Two reactions.

First, I'm blown away that Mitsu replaced your rear suspension when it wasn't 100% clear that that was the problem. No, I'm not surprised that they did some work that had zero effect on the problem. Rather, I'm amazed that they spent any serious money.

Second, a noise from the right-rear that doesn't depend on ground speed (which is what I read your recent event to be) is almost definitely a dying ACD/AYC pump. Normally I would say "good luck" on getting them to fix it, but you seem to have a one-in-a-thousand dealer and regional rep (see first comment above), so maybe you'll be OK.

 

ACD/ AYC pump is an excellent suggestion. He's probably right (usually is) but I hope not.

I was going to ask the obvious two questions:

Did you move your wheels around to confirm it wasn't a wheel/ tire?
Did you change or swap your rear pads and ebrake, and pull off the dust shield?

 

Thanks for those replies. The noise does depend on ground speed. It's usually at very low speed and goes away. Since the straining noise the rotational tapping hasn't been heard. I took the car by mitsu yesterday and they put it on the lift and we did a road test. Of course... the noise wasn't audible. When the car was on the lift, everything looked ok, I was there in the garage with them checking the joints, etc. We checked the ADC/AYC pump, mine is located in the rear right, and all the fluids are good and it seems to be in tact. The AWD system is working properly, 1 wheel rotation = all wheel rotation. I'm pretty stumped at this point because when I started the car up this morning I expected to hear the tapping as I pulled out of the drive way and down the street, but there was nothing.

Do you guys think that if I turn of the ASC system and switch through the AWC settings it might affect it?

We did not pull the pads off or check the shield but the tech said the pads and ebrake were good.

Any other thoughts?

Thanks