Hughes TC in '91.5 W-250
In no way do I mean to flame Hughes TC, in Phoenix, AZ. I will just relay my story.
My 91. 5 W-250 was the biggest SLUG in town. I thought it was lack of power from the engine. Had the pump turned-up twice. Helped ever so slightly. K&N Airfilter and Banks exhaust gave hardly any extra power. Replaced the 21. 5 sq. cm turbo with a 16. That really helped. Had the injector pump recalibrated, off the truck, by Diesel Performance Center in Phoenix. That really helped also.
Before these mods, my max boost was 15 lbs. After, 30+lbs. (only have a 30 lb guage. ). Truck runs alot better, now.
I bought this truck primarily to tow my (at that time) 19' travel trailer. Maybe, 3500/4000 lbs. But, I live in Phoenix (1100'elev. ). I camp in the White Mtns. in eastern AZ (9200/9500' elev. ). So, there's an over 8000' climb in a little over 200 miles. Go to western Colo. on vacations. Even higher.
When going up the grades the truck would not go faster than 45/47mph. Even with the upgrades. You could "floor-it" and the rpm's would go anywhere you want them but, the truck would not go ANY faster. That's when I figured out that it wasn't lack of engine power but, the power wasn't getting to the rear wheels. (My buddies, with Chev. V-8's said it was the lack of power in that little diesel engine). I checked with Hughes TC and they said to bring the stock TC in and they would check it out. Probably the vanes were bent.
Took it to Denny's Trans. to have the TC removed and they did a stall speed test before removal. Stalled at 2200rpm.
Hughes disassembled the TC said it was OK but, rebuilt it with what was supposed to be a much lower stall speed. Reinstalled it and it was much "grabbier" than before. You had to really stand on the brake pedal to keep it stopped at a stop light.
The bad side was that it did nothing for the towing ability. Still couldn't go over 45/47mph, uphill. This was all done at 108000 miles, June '99. Cost $684.
Finally figured out that the lack of a lock-up TC was the problem and started looking for an answer. No one I found knew how to do a lock-up on a first gen. til I met Clint Cannon of ATS. Met him at my first May Madness in Parumph, NV in'02. In Aug. of that year I went up to Wheatridge, CO and had him install his Stage IV Trans. / TripleLok TC. This thing works as advertised. Solved my towing problems. Completely changed the personality of the truck.
The downside, of course, was the cost. Over $6000. Lot's of dollars! But, IT DOES WORK!
I can go up the same grades with a larger trailer ('25, 6/7000lbs) at 55/60mph fairly easily.
It seems like whenever you gain something on one end, you lose something on the other end.
My old, non-lock-up, trans. used to get really hot going up the grades (260/270deg's). The ATS hardly ever gets over 180/190deg's. But, my EGT's never really used to get very high, with the old trans. Now, they climb pretty quickly. The difference is that, now, the engine is "tied" to the rearend and all the power is getting to the ground. The engine, under power, even sounds different.
In Hughes TC's defense, they have had 5/6 years to improve the product I bought from them. Most probably, they have a lot more experience with how a TC works behind a diesel engine. I, at least, hope so.
I would recommend talking to and riding in the trucks of as many people that actually have the product you are wanting to purchase. That way, your chances of being disappointed will be lessened, greatly.
I wouldn't be surprised if there aren't TC's out there, now, that are a reasonable compromise as compared to the cost of a lock-up system. Maybe not a true lock-up, but a lot cheaper, and still work a lot better than the stock TC. I've heard that the DTT-89% is a good example. There may be others that are even better. Since i've never tried them, I don't know for sure.
I hope my experience helps you guy's in your decisions. Boy, this is a long reply. I must have too much time on my hands.
Joe F. (Buffalo)
Attention: TDR Forum Junkies 
), it only hit around 220*. Of course, that was 2nd gear most of the way because the EGTs were too high - something the 4" exhaust helped control. 
