I'm slightly worried about the hub on the back (flex plate) side of the converter. About half of it has a lip around it and the other half is just square. This fits inside the crankshaft for extra stability, I was told. Does this need to be perfectly round or does it not matter. I did look at my stock converter which was taken out about 2 years ago and it looked the same way. Is this something that I should be worried about?

 

The squarish part is facing the flex plate and the round part is facing the transmission. The reason for the squarish front side is because that is where the lockup disc is located, when engaged the input shaft is rotating at the same speed the engine is. Before the lock up converters, the TC where round on both sides, kinda look like a doughnut with the pump drive on one side and the mounting tabs on the other.

 

Not the actual converter, I'm talking about the hub that goes inside of the crankshaft. It's about 1" to 1.5" long.