First of all let me say I'm glad to be a new member and look forward to using this forum. Now to the problem, I have an 04 Z71 tahoe with about 40,000 miles, I've recently started to notice a whining noise coming from either the transmission or engine. I keep up on the maintenance and I've never had a problem with it before. I checked the trans fluid, power steering fluid and of course the oil. I was just curious if anyone else has experienced this problem. Any help would be greatly appreciated.

 

Try taking the belt off the motor and start it up for a minte or so and see if the noise goes away

 

Welcome to the Tahoe forum.

 

Make sure you’re the only one in the vehicle. I had intermittent whining in several of my vehicles…turns out the only time I ever heard it was when the wife or kids were in the truck with me. Taking the belt out took care of the kids but haven’t been able to do much about the wife…[]

 

I had the same problem, turned out to be the power steering pump. Here's an old thread on it:
https://chevroletforum.com/m_3666/tm.htm

Hope this helps.