Strange Sound And Loose Rear End

[sc4sooner]

i have a 92sc4 and recently i have noticed a sound coming from the rear of the car. the sound is almost like if there was a chunk missing out of the tire but there is not i checked all the tires. i know it is from something rotational and tied to the speed of the tires, not the rpm's. also i have noticed when i turn left the noise stops, but also if for instance i am on the highway and i change lanes to the left the back end gets squirly or lose, it almost feels like my axle is sliding.

i have crawled under the car and did not notice anything strange, so i was wondering if anyone had had this problem before, or know what could be causing it. any info would be great,

thank you