Everybody knows that when adding aftermarket parts to the engine and creating more horsepower and torque, a reliable transmission is a must, especially when you’re dealing with a 1999-2003 7.3L Power Stroke. Figuring out whether or not to replace your transmission can usually be pretty easy to tell. Some of the complaints include: shifting hard between certain gears, overheating, delayed engagement when towing, and that’s just a handful of many more. Another sign it’s time to upgrade is when you’re going to be increasing power on your 7.3L. Experts say that if you’re going to be doing racing or towing, anywhere around the 400whp mark is when to upgrade. The stock transmission is only designed to hold so much and almost 20 years of new technological advancements since these transmissions were first built can only help the decision of an upgrade.