Help needed identifying high pitched whine

Hello, we are the 501(c)(3) non-profit Military Mobility, which provides suicide prevention and resiliency training to veterans in need. We use the rugged geographic landscape as a medium for the personnel and professional challenges we face in life and a fleet of 4WD vehicles to literally navigate and overcome obstacles. This provides massive opportunity for positive transformational growth.

Recently, we purchased sight unseen (never again!) a supposed beautifully restored 1997 Defender 300tdi. Previous owner said gear box, transfer box, and axles were refurbished recently. Sure enough the paint and interior is impeccable but it makes a horrible high pitched whining noise while driving. It’s sadly our problem now. Here are the troubleshooting bullet points and I’ve attached a link to several short videos of a test drive and what the drained fluids look like.

-whine only present when foot is actively on the accelerator.
-no whine when off gas pedal, coasting, braking, or in neutral.
-whine present in both high and low transfer case, including while locked.
-whine present mainly in 3rd, 4th, and 5th gear. Somewhat audible in 1st and 2nd but only at very high RPM’s.
-changed fluids in gear box, transfer box, front and rear diff. Nasty stuff (see videos). No change to whining noise.
-removed front and rear driveshafts one at a time, whining noise still present.
-serpentine belts are in good condition and don't appear to be slipping


*We are deeply appreciative of your experience and assistance. This is our first Defender and we are based in rural Wyoming, USA. We do have relationships with some Land Rover specialty shops however these are 10 and 20 hour drives away.

Hi thanks for taking the time to post the pics and vids
my landy is a bit older than yours and I have no experience on that model but does sound like a bearing failed with bits in the oil too
assume it’s not noisy in neutral parked up.
have you checked the pulleys on the serpentine belt are not dry / worn

video seems to also show that whine increases with Road speed rather than revs as it’s the same pitch when changing from 3rd to 4th etc

you could also try posting this thread in the defender forum and also run a search on that too

Thank you Steve, I have updated my post to reflect the pulleys and belts appear just fine. I didn't want to judge too much on my own however the sound definitely seems to be coming from beneath the vehicle, meaning the transmission or transfer case. When you say a bearing may have failed, do you think it is from the transfer case or the transmission?
*I'll also post on Defender forum, thanks