Page "Grimlock" Paragraph 36

The final straw for Grimlock came when he and the Dinobots were injured in a Decepticon trap at an airfield.

Enraged, Grimlock refused to take orders from Optimus Prime any more, and led the Dinobots away from the Ark.

When the Autobots began to suffer from Cybertonium deficiency, Spike Witwicky and his girlfriend Carly attempted to persuade the Dinobots-who continued to function perfectly, as they had been built on Earth without Cybertonium-to steal some of the mineral from a Decepticon shipment coming in from Cybertron.

Grimlock instead opted to lead the Dinobots to Cybertron itself, where they were captured by Shockwave and put to work in the Cybertonium mines, until Spike and Carly rescued them.

Brought back to Earth, the Dinobots agreed to follow Prime's order again-until such time as Grimlock did not feel like it.