Outer Limits 4x4 Board

we are trying to fix the whine in the rocky gearbox does anyone have any suggestions as to what we can do
we have put some LUCAS oil additive in it but to no avail as the whine is still there
can anyone help or does anyone near the sunshine coast have a gearbox/transfer that they would sell cheaply (or give away if it needs repair (yeah i know im a cheap a**))

Did it happen all of a sudden or has it been getting gradually worse over a period of time?

If it's been getting worse over time and it's done much over 200k-250k kms then it's probably due for an overhaul (bearings, seals).
I would expect it to cost $1200 - $1500 for a good quality job.

They're not what I would call a quiet transmission by todays standards.

Make sure the noise is from the gearbox/transfer and not the diff or engine.