well, I have had stock, TCI, and DTT, and I can safely say that there is a definite difference. I pull 12,000 lbs up and over the Rockies with my 300-horse '93 pulling steep grades with the pyro at 1200*, 20-30 lbs of boost, transmission in 3rd, cruising along at 40 mph, and the transmission has never given me any problems. Heat remains in par with the engine, getting up to 235* but never any more, and 235* ain't bad considering. My only issue has been egt's and that is a fuel issue - lots of it.
Without the DTT converter I wouldn't be hauling anywhere near this load with this much power. And, I can also attest that the DTT converters are worth every single penny, even non-lock up. In fact, lock-up has never been an issue. The converter loads the engine good and hard, and the more power you have the harder it pulls.
I'd never recommend a stock converter for any reason. For a daily-driver that does not haul anything major, a TCI (or other non-big dawg) should be good, but for a tug boat, there's no other better way to go.
Ya can't go cheap if ya want to haul the big stuff, and, from all accounts the Suncoast and Goerands clams are on par with the DTT. I have 3 6BT rigs and two have DTT clams, and I wouldn't have it any other way. Fuel mileage goes up, heat goes down, and load hauling goes up. All good.
- M2