I have a 2000 Yukon 4x4 and i hear a loud whinning noise that changes with rpm. I always thought it was the steering pump but last time I had it worked on I was told it was the transmission. It seems to shift fine and fluid level is good. It happens at all times the truck is running in any gear moving or stopped. I also have a small oil leak from an unknow spot. Not enuf to leave spots on the ground but its on the undercarraige and under pressure like when passing it leaks enuf to cause smoke. I dont think its related but thought I'd throw that in there to give as much info as possible.