Whine from transmition?

hi,

My td4 sport has a high pitched whine when travelling. Doesn't really matter what the speed but it's most prominent when you take your foot off the gas or your costing in neutral. It comes down in pitch as the car comes to a halt.

I towed a 750k trailer today and noticed the whine had prett much gone so it seems to go quiet under load.

Could it be a bearing?
Gearbox oil?
Clutch thrush bearing?

Any help would be appreciated.

Thanks

remove rear prop and try it

jamesmartin said:

remove rear prop and try it

Click to expand...

Forgive my ignorance but what will that tell me?

whether ird /gearbox or rear diff ,