Check out the cool set video from Hong Kong for Transformers 4 where it’s said this is Grimlock’s roar.
We hear what sounds like mechanical movement and a roar while set extras run, which could be just for the scene.
Still sounds pretty good, however.
Transformers: Age Of Extinction has a Summer 2014 release directed by Michael Bay and starring Mark Wahlberg, Jack Reynor, Nicola Peltz, Sophia Myles, Li Bingbing, T.J. Miller and Kelsey Grammar.