Transman says that if you disconnect the TCC you will cause the transmissin to overheat, due to the constant slipping of the converter. I have never bought that assunption and the gas mileage will not suffer much because the converter doesn’t lock up anyway until you reach cruising speed, and most cars would perform better if it didn’t. Most cars don’t have enough power to run in “lockup” without “unlocking” on a hill and “locking up” again when it levels out. My old Dodge not only “unlocks” on a hill but downshifts to 3rd gear at the same time, which I don’t like.