My 87 300TD had the right side replaced (me and my brother did it and it sucked) at about 175k and the left side was done about a mounth later.

If you jack up the car and grab the wheel you can feel the play by twisting the tire. If you can feel it moving it is making the noise.

I would have both done. It will most likely be expensive.
Special tools will be needed or it can be done carefully with a cutting tourch.

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82 Rabbit diesel (first d), 84 Jetta turbo d (300k when sold), 83 240d (305k when sold), 84 F250 6.9d w/Banks turbo(parts truck), 86 F250 6 cyl.gasser(waiting for 6.9d), 84 300d ( 347k Sold 8/04), Y2k New Bettle TDI (185k miles), 95 740IL (wifes), 87 300TD (206k Sold 7/05), 05 Passat TDI Wagon