99 silverado 1500 5.3l 4x4 automatic - No reverse. When I place the truck in reverse, there was a whining grinding noise. When driving, anything over 10mph causes grinding whining noise, Thought it may be it was a problem with the transfer case. I pulled the transfer case out. Everything seemed fine with the transfer case, although I noticed it was a red fluid in it, the fluid I got form the dealer was blue, possibly transmission fluid? I spun the output shaft on the transmission, and the grinding noise was in the transmission. Truck in park, I could spin the output shaft. I started the truck and the output shaft spins on the transmission while still in park. Put it into reverse for just a moment, and the grinding was there, Am I needed a new transmission? Or maybe some kind of external sensor? There was no load breaking noise or any event that would cause alarm leading up to the problem. Any advice/ incite is greatly appreciated.