It sounds like a programming issue, you need a sled program that either leaves the TC unlocked, or sets it at a high enough speed not to bog down. Or possibly program it to delay the lock at WOT to a higher mph.
I have a similar issue when towing really heavy trailers; if I use too much throttle from a stop, the TC locks prematurely (at the same time as the 2-3 shift) and bogs the motor. If I use light throttle, it stays unlocked well into 3rd gear. I'm not sure what the parameters are for the lockup, but throttle position definately effects it.
I'd guess engine rpm/input shaft speed should be close to eliminate bogging down at lockup but how to achieve this through progamming is beyond me. /ubbthreads/images/graemlins/shrug.gif
Or you could use a heavily modulated lockup and "slip" the TC to reduce bogging but I don't thing the TC would hold up very long doing it at WOT.
An extremely low stall converter could help this condition as well, as it would not allow a large speed differential between the engine and input shaft.
with mods below, 3:73's, 305/70/16 good year MT/R's, 8000 lb. stock class. the truck will NOT run 3rd gear. tried it a few times, not enough power. i do not have a tc lock up switch, but i can say that when pulling, sometimes the tc will lock up and sometimes it wont, when it does it makes a big difference in ground speed.
also, i noitced that doing "boosted launches" seemed to help me get enough ground speed, quick enough to get the t/c to lock. if i just roll out easy and squeeze the pedal to the floor it never gets going fast enough to get it to lock. my truck dynoed in august at 328hp. maybe with 400 you could run 3rd, but not 328.
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Wouldn't third gear in 4 low be about the same as 1st high. You just have the extra 2 gears down low if you start bogging and you have some help getting the rpms up when getting the sled going.
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It's pretty close, I just thought the big horsepower guys used HIGH range for wheel speed.
I don't want to think about the amount of power going through the LOW range gears of the TC with the transmission in the lower gears.
I'd think with proper axle gearing, you could use HIGH range and take the load off the TC gears which would be the weak link.
The fewer gear reduction sets you run the power through, the more power ends up at the wheels. Which is the reason most dragsters have gone to direct drive (no transmission) with the only gear reduction in the axle. Of course this would only be practical in a dedicated pulling truck.
Just thinking outloud...
I haven't been inside a 271 to see the gear set, but if guys like bbunting are running in LOW range, it must be pretty robust. Running in direct (HIGH range) would be more efficient though if you got the axle ratio right.
The problem pulling in drive with just a slighty modded truck is that if you start to bounce and have to back out of throttle, the truck downshifts into 2nd. Pulling first gear high range is about the same as pulling in drive buts it pretty easy to get under the turbo as the sled catches up. Another thing to watch is your competition. If your at a pull with a lot of big power trucks that are stopping 275-300, with a lightly modded truck you dont have enough track to let the truck get into drive and take advantage of the wheel speed before the sled hits and shifts the truck back into second anyways. Now if your in a true "street" class where its all trucks with chips, tuners, etc and stock or very mild turbo ugrades and the sled operator as the sled set accodingly, yes drive is the way to go. I my self almost always pull 2nd gear, convertor locked.