Well NOW I have smashed a clock with a hammer but the casino would not let me take apart the slot machine.
I don't have anything to compare it to but the ZF has worked for me and I like the retarder --- The support from Harbor Diesel in CA has been very helpful and quick.
Kept me from using a tow truck and got me off the side of the road with a little tech help over the phone.
In the years that I have been reading this I have heard that the ZF is a superior trans. Why? Dunno. My impression is that the reason people stay away is the cost to repair and scarcity of qualified techs. You have beat that problem. From what I hear you will not outlive that trans and that is considering you will live a long long life.
You add in the cost of a 740 core and the labor to r&r and I bet you are close to what you paid.
Good luck with your "new" trans. Let us know how she does after a few miles.