The truck was used by the previous owner for dropping boats in the water. I have 84k miles on it. I only tow with it so all 84k miles are towing. I do change fluids but the rear end developed a whine at 81k miles, that I feared towing with. I think there was water intrusion at some point before I owned it.
So I had east coast gear rebuild it.
The transmission did not have a factory cooler on it.
When I went to drop the pan for a fluid change , the bolts that were open on the top of the trans case we're so corroded that they snapped off.
So with several bolts snapped off , on a transmission that had towed a lot with no cooler, I decided to just have it rebuilt. I could afford it, and it eliminated worry about an on the road failure. And even if I get a newer truck, I'm keeping it or giving it to my son.