If your torque converter isn’t locked up when the exhaust brake is applied, you’re only benefiting from a fraction of its retarding power. The BD AutoLoc commands the torque converter to lock up, and stay locked up, any time the exhaust brake is applied in third and fourth gears. This not only helps with engine braking, but because there’s no clutch slippage, transmission oil temperatures remain low. The lock-up clutch and exhaust brake automatically disengage at low speeds to prevent stalling and transmission/converter damage.