07 Z06 strange noise

[carsdif]

hello , I have a strange noise like a little knocking (toc .... toctoctoctoc) coming from under the car , don't know exacly , I ear this noise only when I speed up very very srtong in first and second gear , in straight line and when the gripp is good
the car have less than 5000 miles , 6 mounths , i've change my diff oil with additive , but it doesn't com from it.... transmition axel??don't know ... help!!!