Whinny noise from diff, area

[Odie]

Ive just had a new noise appear from the diff kinda area of my car, a whiney low noise. Any suggestion of where i can have a look to see what it is?

[PlayersNo6]

Has the rear diff oil been changed yet? Due at 6 years or 54k, same as the gearbox oil.

[beeblebrox]

Does the noise come and go if you load up the drivetrain and then let off the throttle, etc? Does the volume/pitch vary with speed?
Perhaps a wheel bearing is on its way out - does the noise change if you gently zig-zag along a straight road to alternate load on the wheels?

[Evangelion]

Whiiny noise ... you mean it sounds like a horse?

[/phgrammarpolice]

[Odie]

Ive still not pinned this down yet, it went for a day and is back again.

Its done 72k and ive not changed the diff oil, I'll do it over the weekend see if that helps.

My rear brake discs are also in a shocking state so it could be one of them, im kinda deaf in one ear so im having problems pin pointing it to a side while driving, i will have to stick it up on a jack and check the bearings that way.

Anyone got a link to a guide on doing the wheel bearings, Ive done it before on an escort (fronts and rears) is the mx5 any more problematic?