I recently rebuilt the power steering pump on my 1990 ls400. I haven't had any problems with it as far as function, but it had begun to leak. I thought the rebuild was pretty straight forward. I replaced the main bearing as well. Put the pump back it in, refilled ATF, etc. Works fine, BUT, now there is a small vibration in the steering wheel between about 700-1000 rpm. Every thing looks ok, no noise, pulley spins true, etc. Any ideas?

 

Maybe some air in the system still.