No. My Freightliner had it. It just plain rocks when hauling. Flip the switch, step on the brake, the engine slows the truck down instead of having to burn up your brakes. Coming down the Rockies just sucks without it. Wikipedia: An exhaust brake is a means of slowing a diesel engine by closing off the exhaust path from the engine, causing the exhaust gases to be compressed in the exhaust manifold, and in the cylinder. Since the exhaust is being compressed, and there is no fuel being applied, the engine works backwards, slowing down the vehicle. The amount of negative torque generated is usually directly proportional to the back pressure of the engine. Since diesel engines lack a throttle valve on the intake manifold, there is no intake vacuum when the engine is not using fuel. The intake vacuum creates the drag effect felt in gasoline engines when going down a hill with the throttle closed.