You may well have, probably do have, a damaged bearing that is making the noise.
This will just get worse and worse until it breaks, or until it is so noisy you have to get it replaced.
Making it quiet is only a short term solution, you really need to get it fixed.
Having said that you may be able to keep it from getting worse for a short while by adding a modifier to the oil. One I could suggest is Molyslip ATFA. It should not hurt to try a tube of this stuff. If it does not work, then plan on replacing the bearing.
http://www.molyslip.com/Products/MolySlipATFA.html
CAUTION: Do
not use Molyslip friction modifier for manual gearboxes in your differential. This will cause the LSD to stop working because of no friction. Only use the one mentioned above.
Also please note you act on the above advice at your own risk.
The correct thing to do is replace the noisy bearing. Best of luck with it.
Joe
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