Not trying to be nasty or not try to understand the problem at all, just simply stating how a diff (especially in a straight line) seems unlikely to cause shudder, not saying its not somehow possible, but there needs to be some better information to attempt any sort of help. The dealer has told him its the LSD causing the problem, and also told him its normal, do you suggest it's normal for sn LSD equipped car to shudder on take off?