Master Mechanic is a utility gear perk that boosts your repair tool, repairs vehicles while you sit in them and lets you fix auto-turrets. It is a big help for vehicle-heavy play.
Your repair tool works better and your vehicle heals while you drive it. You can also patch up auto-turrets.
Very good if you fight from tanks, armored cars or helicopters. Foot soldiers will use it less.
Heavy Hitter helps you win vehicle fights while this keeps your ride alive.