Its got a turbomaster (a real one) and the spring is turned down to about 2.0 inches, it doesnt get to 12..it climbs to about 8-9-10...11...then pops off and falls to about 8.
PErsonally, I originally thought that the WG valve was sticking, it builds boost so slowly....
Its got a 4" Diamond eye, 3" downpipe, 2.5" crossover, Spectre filter, 125K original miles.
What could cause the trans to do what it does..and also cause me to lack low end power? I pulled the glovebox out, and the computer at least appears to be unmolested.
Factory calibration sucks for pretty much anything besides daily driving or light towing (and I mean light) is probably what you're dealing with.
The factory calibration also is biased towards mpg.
Here's the lockup behavior on a stock cal:
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You also need 72% TPS in order to make it shift down from 4 to 3. That's 72% that the PCM sees, that's not necessarily how far the throttle pedal moves. The stock cal also tries to crowd as much of the engines power down in the low end as possible, at the sacrifice of the upper end. What you get is a truck that "feels" snappy because it's crowded 75% of it's power down in 25-30% of the throttle. But it gets pretty lame pretty fast as you get deeper into the throttle.
The stock vacuum system holds it down around 5-8 psi by a PWM signal to the wastegate solenoid. Essentially, it rapidly "flaps" the wastegate until just bleeding drive pressure off isn't enough and then it opens it.
I've got a Heath TM on mine right now, but I prefer the stock vacuum system. Programmed right, it gives you more control over the turbo behavior and will build as much boost as the engine is capable of if you tell it to.
With the vac system, I can add boost (or take it away) at any point of the curve I want. The TM is either open or closed.
The movement of the wastegate also helps to keep it from seizing up from rust and/or soot.
I'm running Bill's TM since my vacuum pump died and I am a bit short on cash to buy a new one. I had Bill's TM on the shelf so it's doing stand in duty until I can get a new Delphi unit.
That's just my preference though.
Since so few can adjust the calibration on these trucks, they tend to look for "old school" solutions. It's possible someone has been mucking around in your transmission with line pressure "improver" kits and other assorted whatnot. This messes up lots of things on an electronic truck since the PCM no longer is getting what it's calling for.
Of course, you truck could be behaving normally and I just can't tell from your description. It's kind of one of those things you have to see and feel to troubleshoot....
