I'm in CA and selected ProBuilt Transmission in West Sacramento for the rebuild. Crawling into the world of Transmissions, at first was overwhelming...shop rebuild vs remanufactured. Initially was headed towards remanufacture (Certified Transmission due to 100K mile warranty) and ship to an installer. However I learned not many shops will install another vendors work. Also their advert for heavy tow is listing parts upgrades already used in the 2015 6L90.
The owner Don (Probuilt) was very open discussing my observations and quickly narrowed the culprit to the torque converter, then confirmed metal grits in the pan. Don took the time to walk me through the tear down. Showed where it failed, how it failed and why. Spoke of the thin converter wall heating and causing a wave the plate rubbed against, migration of metal between the pump and housing, how it wore pump vanes. He was shocked the majority of clutch plates were in good shape and knew I took effort to keep my transmission on a partial fluid flush and filter replacement schedule. In a world that says "Due to insurance regulations no customers allowed in the shop" signage, Don insisted on showing me his work place.
Don also spoke about OEM design and engineering vs. bean counter restraints and what he does to rebuild transmissions, which I'll list in the rebuild post.