[reptar_head]

I doubt the rear axles are at fault, I've never seen an axle cause a high frequency vibration, they're always really hard thumps. I'd say you get the car off the ground and run it and see if you can tell where it's coming from. After that, pull the driveline and run it in the air, since it seems that no one has actually done it, we're just guessing as to what will happen. If fluid start coming out, shut it off and we'll know you can't do that, no harm done.