my fj80 has a six inch lift and 35's. It has developed a nasty vibration after being driven for a while, like it has to heat up what ever is causeing it. I have a c.v joint in my front drive shaft so I know it's not an angle issue. But for kicks I removed the front driveshaft, locked the center diff and the vibration goes away. I was told that the all wheel drive uses a viscous couplong of some type, and that it may have issues, any more inclusive info or advice would be great, any other info needed just ask thanks a great deal!!