X2
Classic diff whine.
Just change your diff oil if you havent to make sure its ok.
They can sound like that for 100's of k miles.
Its not worth the trouble of a rebuild until you cant hear the radio over the whine.
I hope you intend on having the car up on a hoist for a good look over before you leave on your trip.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving