[low 84]

if the connection is on the dirver side of the tranny, then you probly have a lockup torque converter. what is does is above a certain speed it locks the engine and transmission up solid trough the torque converter. this gives you better gas milage on the highway becuase your input shaft on the tranmisson is turning exactly the same speed as the engine, with the converter not locked up the tranny does not get 100% of the power from the motor due to the inefficientcy of the torque converter.

with this being disconnected your transmission just won't lock up at higher speeds, which dosen't hurt anything, alot of th350's are like that from the factory. it shouldn't effect your downshifting either. i think your problem is somewhere else.