You'll never get the same amount of reliability out of an upgraded gasoline car transmission compared to a downgraded HD truck transmission. It's part of the reason modern engines, and our diesels, last so long: Detuned/or derated for longevity. (And, on that note, the transmissions in the POS Ford Transits, which are basically really tall Focuses, my employer decided to buy as work vans are on their way out...)[/QUOTE]
For sure, the torque comes on much quicker in a diesel & kills a gasser tranny that's put in behind a diesel. Many guys upgrade the autos behind a Cummins so they can hold the power, at least a valve body upgrade. But even a stock Allison can't hold the power of a modded Duramax.
The bad thing it's getting impossible to find a manual trans anymore for a brand new vehicle esp trucks!