Wheeljack is one of the roughest Autobots around. As one of the last surviving Wreckers, he's seen plenty of action, and he's got the snarky one-liners to prove it. If there's anything he likes more than slicing up Decepticons with his swords or inventing new gadgets to blow up Decepticons in different ways, it's hanging with his old buddy, Bulkhead (who calls him Jackie).
Wheeljack doubts Optimus Prime's leadership capabilities, believing he's more of a stuffy old figurehead than a warrior. Wheeljack also chafes under too much supervision, which immediately puts him and the authoritarian Ultra Magnus at odds. That's why he usually takes off shortly after he's arrived. He'd rather be on his own.