LT1Formula26

I am having the wierdest **** go on with my ta. I have always heard this slow howl when i have been driving the car for about 10 minutes and slow down to about 5mph to turn sharply. Once I turn, i hear a couple of clicks from the back and then its all gone. When I have been driving the car for a while and I come to park it, when I turn down the music I hear like a quiet whine from the inside of the car, but not really from the outside by the rear...only inside. It sounds almost like the beginning sound of the tornado siren but not loud. It has done this many times before and all of these symptoms:
1) Have been going on for a long time
2) Only happen after I have been driving it for a bit.

Is it time for a fluid change?....I opened the rear up and it was really full. So maybe the fluid they put in doesn't have slip additive?

Any suggestions? My ABS INOP Light comes on and off during driving also.