Suzuki: suzuki, Samurai, suzuki samurai, rear tires

Question
i have a 1988 samurai, i put a lift kit on it about 3 years ago. now it starts to vibrate and shake when put into 4high or more in 4 low,my front and rear shafts are not in a bind, could this be a transfer case problem? thanks

Answer
The question you need to answer is whether any of the selector sticks vibrate wildly.  That would tend to point to a u-joint at the gearbox whose stick vibrates.  If the whole vehicle vibrates, it would point to an issue at the front/rear axle.
Compare the front and rear tires, are they the same circumference?  If the tires are worn unevenly, that could be the source of your troubles.
Worn/broken transfer case mounts could also be a source of troubles.