LT77 whining on deceleration

Hi All,
Seen a couple of old posts on here relating to whining, mine is a LT77 fitted to a 300TDI on a 90 Defender, it only happens when I take the foot off the gas i.e. approach to a roundabout/giveway, it's not a deafening sound, but loud enough and very annoying.
I've taken a sound recording on my phone, but can't see how to upload this, any ideas?
Anyway, it sounds like (but I guess it's not) the release bearing spinning, a high pitched whistling/whining/spinning noise.
Only happens when clutch is out and when decelerating.
Any ideas appreciated, Steve

sure its not a diff

jamesmartin said:

sure its not a diff

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Hi James, thanks for the prompt response.
Not sure at all, sounds like it’s coming from box area, but I guess the noise travels.

I will try and get the front prop off first and give it a spin with Diff lock on.

If I could upload the sound file, you would hear that the sound sort of bounces, don’t know if that helps.

feel for any loose play in the with the diff flanges

Right, got the front drive shaft off, not run it yet, ran out of time, There’s about 25mm diff flange rotation at the bolt hole diameter, sounds very ‘clunky’, Is that normal

Now had both props off, separately, and tested in diff lock, whine still there!
T Box was about 500ml short of oil, now topped up, gbox oil ok as are both diffs, whining still there on decelerating!
Any thoughts about how I can track down the source?

if you eliminated both diffs,its obviously one of the boxes, id remove t/box sump plate and check for play in the intermediate gear plus the input and diff carrier