Backstory: took my vehicle (2017 Tahoe) in for basic scheduled maintenance - no issues. Had the transmission flushed at 97k because we were advised to do it before mileage hit 100k. Within a week after the flush, my truck sounded like a tractor. Took it back to dealership that did the flush. They stated the mechanic thought the seal would be ok when he did the flush but it is a high mileage vehicle and the seal leaked. We paid to replace the seal and they refilled all the fluids. The truck ran ok on the way home but soon started making noises that continued to get worse until the transmission wouldn't shift at all. Had it towed back to dealership. They now say the torque converter is bad and want to charge me $7200 to fix it. Could their initial mistake of not replacing the older seal they "thought" would "hold" and then all my fluids leaked out have caused this? $7k is a lot to fork out after they've had it twice already and possibly caused this. Please send your thoughts on if the two are related and if one could have caused the other.
Low fluid ( half empty) in the torque converter might cause problems for the many thin steel turbine blades, but I think it is unlikely. ( Long ago, working on automatic transmissions , it was not unusual to find bent turbine blades in the torque converters, a loss of efficiency but they performed relatively normally). Much more likely is low fluid cause low pressure on the servos that apply clutches and bands; low pressure permits them to slip. Abnormal slippage like this can burn/destroy the friction linings in a few minutes. A relatively moot point; improper service caused failure of the transmission regardless of the failure mechanism.