During retraction, some of the hydraulic pressure used for retraction is ported to valves which activate the brake system to de-spin/brake the wheels. The 747-400 "autobrake" system per se, is not used to carry out de-spin.
It's all done with mechanical valves. I suppose there could be faulty components, leaks, etc. It wouldn't hurt to tell someone about the unusual noise, especially if the person is a frequent flyer like Mrs-Flo.
Did the noise continue well after retraction?