Rear Diff Whine?

[grelise]

So, travelling to work today and I noticed a whine coming from the back. It was still there coming home. A workmate I was taking home noticed the same whine and asked if it was the diff. He mentioned something about a head plate?
Not sure, but, anyone got any ideas? Had the same symptoms? It is most evident at 100km/h and reduces in pitch with reduction in speed.
I had a quick look in the service manual, but can't find anything.
I change the diff oil approx every 20,000km.

[Madmagna]

What diff oil do you use

[grelise]

The recommended SAE 90 by Castrol.

[munkeymanz]

You sure it's not the tyres? Just a thought... Diff whine noise would be very apparent under acceleration/load at speed?

[grelise]

Quite sure it's not the tyres, they are only 10k old

[Madmagna]

Have you been using proper LSD fluid, I personally use diaqueen from Mitsubishi

[grelise]

Yeah, it's proper fluid, I'll check again.
I'll even give the Diaqueen a shot, see if it makes a difference.

[Madmagna]

Once the damage is done nothing will fix the noise unfortunately. I generally would not do changes every 20k personally but then again the only downside to doing this is that it costs you more.

May just be a case of bad luck perhaps, even if you did not use the correct fluid this would have more effect on the clutches in the LSD than the bearings or the crownwheel and pinion.

When you did the last change, what was the condition of the fluid.

[grelise]

The fluid came out clean and same colour it went in. No indication of any flecks or chunks. On the weekend, I'll get under the rear and check all the mounts and condition of it all.

[macropod]

FWIW, changes in pitch are also common with worn bearings and tends to be there regardless of load (acceleration/coast/deceleration). Diff whine tends to come & go with changes in load.