Jackaroo Differential

I have a 99 model Jackaroo SE Auto Petrol which has travelled 50000 K's. During the past week on 2 occasions within 5 minutes of each other I noted a shudder(thump-thump-thump) through the vehicle just after take off from a tight parking spot. The indication was as if I had a flat tyre on the passenger side rear. Tyres were OK so I checked to see if I had picked up a large stone & then checked wheel nuts - all OK. A friend suggested it might be due to the limited slip diff sticking and it should not really be a problem. Since that time have done ca 1000k's without it occuring again. My Holden Dealer has said he has not heard of this happening and suggested that if and/ or when it happens again that I take note. I think my description describes exactly how it was! Maybe someone can throw some light on what might be the problem?