Hi.
My Evo IX is suffering from a horrible rear diff whining noise, specially under load. I have the shop change oil and the oil that came out was purple ( I guess it was Royal Purple since the shop that did the maintenance loves those oils ). The put new Royal Purple diff oil and the whining sound is still there.
Do you guys think it is the oil? Should I use Diqueen ?

Today they checked all the nuts and bolts in the drivetrain and they seem to be ok. I am afraid that the gears will wear out.

 

Hi,

By rear diff, did you mean the actual rear diff (LSD / gear fluid) or the AYC clutch bath (SAYC or ATF3 fluid)?

There have been claims that by changing the rear diff fluid, the whining (or otherwise known as the infamous donkey noise) would stop BUT there have also been claims that changing the AYC clutch bath has fixed it.

If you are like me, just change both since it isn't great to have very used oil/fluids in both systems.

I would suggest for you to get your mechanic to drain and refill the AYC clutch bath and then see if the issue persists. If it does, then try to change the rear diff fluid to the Mitsubishi Diaqueen fluid.

By the way, the mechanic I use said that the Evos he had the pleasure of servicing never responded well to Royal Purple... may upset some people, may not but that is just something I want to throw out there. Since I am not a certified mechanic, I didn't go against his word and have always bought and brought in my own AMSoil fluids. I must say, AMSoil has made my Evo run impeccably.

**The noise is the donkey noise, correct? Usually happens when going slow around a corner**

 

It sounds like a siren. And when I said rear diff I did mean the rear diff LSD fluid.

I will try using Diaqueen tomorrow and see if that helps. The car only has 25000 original miles. Basically street use with no abuse.

 

I usually change every 3500 or 4500 miles just because it starts looking really bad really quick. If the change to the stock fluid doesn't fix it... Try changing the AYC clutch bath. If you are bringing it to a Mitsubishi dealership, tell them to change the AYC torque transfer mechanism fluid, and confirm it is Diaqueen ATF3. Many will not recognize the what the AYC clutch bath is because the manual will say the AYC torque transfer mechanism.

 

Thanks for the good advice. I will keep you posted.

 

Do you have AYC or a mechanical diff? What affects the noise?

I'm guessing a mechanical rear diff (USDM) and the noise gets louder as you go faster.

If so I'd say your pinion bearing is toasted. You can test by disconnecting the driveshaft and the axles and rotating the pinion by hand. Smooth good, rough bad. In my opinion I would not blame the fluid. Mine failed on OEM fluid and I've been talking to another user who's failed on a different fluid again. My thoughts are that the pinion bearing is prone to failure and you get a good one or a bad one out of the factory. Remove, repair and reinstall.

 

do you know the specs for the pinion bearing? A part number or a size I could ask for at the local auto shop?