GM-GMC: torque converters, high performance engines, torque converters

Question
will a torque converter cause a transmission to shift hard or not shift at normal shifting speeds? Thank you.

Answer
It could, but the transmission would have to be very low in fluid.

Generally, it is the transmission that fails.  Torque converters can fail but they do so very rarely.  The converter failures are usually caused by high performance engines being used in racing applications.