Exhaust Brake – What is the effect of an exhaust brake on the transmission?
A. Exhaust brakes are widely used in the medium/heavy duty truck market, and Allison publishes guidelines for integrating exhaust brake controls with the TCM. This integration is necessary so that the transmission can alter its shift characteristics to maximize the exhaust brake’s effectiveness and not adversely affect transmission operation when the exhaust brake is not in use. Allison Engineering has tested one manufacturer’s aftermarket exhaust brake on a Duramax equipped pickup. This installation was made per the manufacturer’s instructions and had no provision for communicating to the TCM when the exhaust brake was in use, and thus resulted in harsh/objectionable shift characteristics and a negative impact to grade braking performance when exhaust brake was activated. The benefit of the exhaust brake was also lessened in certain circumstances due to the lack of TCM integration.
