Sorry did not make myself clear.

There is an oil pump within the auto box. It has a pre filter which can get blocked which can cause issues with the pump and sometime whining.

I am no auto box expert though, just a though X5 40d

Fixed my problem……

Bit of a stupid thing, mine seems to have been caused by the absence of the 2 rear engine cover rubbers.

I noticed the other day that they were missing and ordered some replacements for a mondeo and now they are fitted the noise has gone.

Ffs, been listening to the buzzing for years and finally it has gone. I’m not saying it’s your issue, but it’s worth pulling the engine cover off and seeing if all 4 are present!! There is nothing that can't be fixed with a hammer😜😜
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I'll check that thanks.

Great that you've sourced and fixed your noise.