Check your diff and diff mounting bolts. sounds like a problem i had,ended up being the diff was old not well maintined and my subframe was cracked in various places. i had to replace diff and subframe. reinforced subframe in the process. no more noise 4 me.
1. check areas around diff like the subframe and mounting points where the diff mounts to. 4 in back, mainly the 2 in front to driveshaft. they are grade "10" blots, also check the U cradle part above the differetial "nose" to driveshaft. these areas tend to crack esp in manuals due to tq.
http://www.supramania.com/forums/sho...%28finished%29
http://www.toyota-supra.info/forums/...eleration.html
2. take rear diff bolt off, stick your finger in the hole and feel the fluid level. should feel fluid right away. if you have to feel around for oil u need a change/refill.
(also lsd uses friction additive in the diff gear oil.) drain diff oil and refill with lsd oil until it almost wants to come out of the check hole. replace plug. should run alot smoother, quieter. why not anyway.
3. with wheel bearing just get access to them, remove the bearings, buy 4 new ones and new grease, put a good amount of grease in the palm of your hand and smash the bearing into the grease in a scooping motion which forces the grease to bead through inbetween the bearings. wipe eccess then reassemble. neat trick i learned from my bro.