Trans Temp/whine

[andyinhilo]

I have a 2008 2500 Silverado 4X4 with the 6.0 and a 6-speed auto and about 6000 miles. It is a Law Enforcement patrol vehicle, and as such does a fair amount of idling. I got it in Nov. of 08 and no trouble till now. I have periodically checked the trans temp and I have never seen it above 155, and rarely that high. This weekend we began to have regular seasonal temps here of 80-85 degrees after an unusually cold winter and spring. I was doing some routine patrols and had stopped to talk to some folks for 15-20 minutes and left it running. As I drove away it began making a loud gear whine. Same sort of sound as if it were in 4 wheel low range. I checked the trans temp, it was 169. Checked fluid, full and clean. Idled in neutral a bit, both temp and noise stayed the same. Drove a bit at 40-50 mph, and the temp began to drop, along with the noise. After maybe 10 miles the temp was down to 163, and the noise was gone. No more noise that day and temps remained 155-159.

 

This morning all was ok until idling for about 5 minutes, and when driving away the whine was back. Temp was 159. Within 5 minutes or so no noise.

 

Is this normal? Our local Chevy/GM dealer was closed by GM, so there is no one to ask, and I don't know what to do about warranty now.