Rear noise when turning on slow speed

[johan]

I bought a 1998 JGC limited with 160000km or 100000 miles on the clock a week ago. It have this intermittent problem - Sometimes at pull away, when the car is hot and the front wheels are not straight, I hear this chuncking or clicking noise from the rear wheels - almost as if the brakes are sticking. It goes away at higer speeds. As I said, this is intermittent. Someone suggest it can be the viscous coupler and by changing the fluid, it will be better?? A local dealer here in South Africa think it can be the clutch system in the rear diff???

Any suggestions will be appreciated.

Regards

Johan