Here is the post I did recently.
It will explain alot about autos and Torque converters.
There is alot of misinformation and wise tales out there so soak this in.
This is the lowdown facts.
Here is quick rundown on TC basics.
Number one you need to decide what you want.
Mileage and drivabilty or Torque and raw acceleration.
You cannot get without giving.
Number two you need to match your cam and TC stall.
You will need to know your Cams torque and Horsepower curves.
(Dyno 2000/2003 is perfect for estimating this)
For "Acceleration" you will need to determine where your peak torque occurs in relation to RPM. Also you will need to determine where your Peak Horsepower occurs in relation to RPM.
As an example:
My 289 and cam the Torque peaks at 5500 RPM and the Horsepower at 7000.
Horsepower will "Pull you thru" the loss of Torque. This equates into acceleration. If you have a cam with a flat torque and horsepower curve then you will not accelerate because the torque is acceleration. If you reach your torque and flatten out you will not continue to accelerate. Your engine will "Bog" at this point because you do not have torque continuing to rise.
(Yes I am going to hear about this)
Here is where the TC comes into play.
All TC's are rated at Flash Stall. This is the RPM that the TC slips to before it starts its lockup. The actual Lockup occurs appx 500 RPM lower after it Flashes to the rated RPM.
So during your shift from gear to gear you Flash to the RPM. What you want the TC to do is to Flash about 1000 RPM below your max Torque. So in my example I would want my TC to Flash about 4000 RPM. This way the Torque after the shift will continue to accelerate my vehicle as opposed to flattening out.
The Horsepower will carry me thru the shift until I reach my Flash again.
Now that is Pure continued acceleration.
Here is the give and take portion.
If I have a 4000 RPM Flash Stall then my actual lockup would be appx 3500 RPM.
If I am using the vehicle as a daily driver the lockup of the TC at 3500 RPM would place me at what speed while I am piddling around town? With my setup of a 3.55 rearend in 3rd gear (1:1) with a 26 inch diameter tire this lockup of the TQ (3500) does not take place until 76 mph (use Virtual Engine Calculator to figure this).
This does not equate into milage and drivability at all.
So I must compromise.
I want my lockup to occur around 40 mph (which is the average speed I will be driving around town). For this to happen I will have two choices.
Lower my Lockup RPM with the TQ which will affect my acceleration performance.
Or lower my rearend gearing.
Or Both.
It is a compromise situation.
The best all around compromise for my example I feel would be a 4.11 rear gears and a 2800 RPM Flash Stall TQ.
That places me at appx 40 mph lockup for drivability at the cost of max acceleration.
Give to Get.
Now you want tire spin?
There are alot of variables as you can see.
With the new
Stang there are more things to consider also.
The 05 has a lockup TC installed. This is a good thing.
It will lockup at a lower rpm to provide mileage.
This is controlled by the computer.
Here is something else new...
Were you aware your new
stang is a Throttle by wire system (Like fly by wire in an airplane)?
Ever try to find that throttle cable? It aint there...
Ford has stepped up to the plate on this new
Stang.
With this new
Stang the throttle, cam, ignition, fuel system, and auto
trans are all tied together and computer controlled.
If you ease on the throttle the computer adjusts the throttle body, cam degree, and auto shift points to achieve your desired response.
Floor it and the computer opens the throttle body wide open for max airflow, the cams will adjust to provide low end torque, and the
trans will adjust its shift points to keep the engine within its torque range, and the converter is allowed to flash to its stall.
Ever notice how your shift points change when you floor it as opposed to just getting on it a bit?
Well Take Notice people!!!
This is technology a step ahead of the competition.
I got an auto arrr you said?
So do I and wouldnt trade it for the stick for nothing!!!!
Although I do find the shift a bit sluggish for my taste, but that was done for the suit and tie pansy that wanted a "confort car too". Easy fix that a transpak will correct some day.
Here ia little more info on the 05 GT.
Max torque is achieved at about 3700 rpm (this is where the curve flattens out). Max Horsepower at around 5100 rpm.
The GT power curve is a bit flat for a drag car but economy also had to be considered by Ford too (Damn Liberal Feds).
But this can be corrected by the aftermarket.
Cant outshift em and it never misses a shift either.
Still mad about that auto???
How do you get a good drag takeoff in an AUTO? 
I think you misunderstood what I was saying. When I say power brake, I do NOT mean cook the tires. I was talking about hooking up and launching, NOT peeling tires. I mentioned to only slightly hold the gas while holding the brakes, not enough to break the tires loose, just enough to get your engine up to the RPMs where you wanna launch from. This means intead of having a split second delay from when you mash the throttle at launch, you take off immediately, and it really helps a lot. Roasting the tires like that is a pretty dumb idea, it'll cook the rear brakes, as well as the entire driveline.
