I was looking at buying an AOD for the car I am building and contacted a performance transmission builder. I gave them all the information needed to determine the right stall for the engine, cam, compression, gear ratio, and tire size combination. They came back saying I needed a 3500 stall in the converter due to the altitude the car is at. We live roughly around 5,500 feet above sea level. My question is this is the first I have heard of elevation affecting the converter stall in a car. I asked them to give me a better explanation and this is the reply I received. Tom, Though converter principles are based upon fluid flow and line pressures, because of the extreme altitude of Denver you have reduced cylinder pressure which will result in lower torque multiplication numbers down low, or at lower rpm’s which will cause the converter to act much tighter than it actually is. In racing applications we have seen some converters loose as much as 1800 to 2000 rpm’s at Bandimereraceway. Thank you, Scott Does this make any sense to any of you??? He says it will equate to 2500-2600 stall.
Contact Performance Automatics, they know AOD's inside out. My first converter was a 3500 , and it was dead outta the hole, especially with the way the AOD works, I'm now running a 2500 non lock up, and it's much better.
That is what I figured the converter I would need would be around 2500 non lock up. When they said 3500 non lock up I was definately puzzled.
With my AOD I ran a lockup Precision Industries 2600 Stallion in my Trick Flow headed/cammed T-Bird and always wanted more stall... I have a 3500 waiting for the 331 using same cam and heads(both are lockup)... Key to using a lockup AOD in a performance application is run at least a 3.50 gear, and 3.73-4.11 is probably going to be better(I have 3.73)... Nice thing about the lockup is no matter what stall you have, once it shifts to 3rd it's in 60% lockup and in O/D it's 100% locked, that's why gear choice is so important...
The engine builder said that we should get 450-460 HP out of the motor 10:1 compression. The cam we chose to run is 226/234 .544 Lift 112*. Wheel size is 245/45/17 and gear ratio is 3.89.
What he is saying is your motor will be making less power at altitude so you need less stall. Sounds to me like he knows what he's talking about. That same converter in my car might stall 5000
Thanks for your comments. I never realized that an advertised stall would not actually be the stall of the converter but that your horsepower of the motor will change the stall characteristics of the converter. Now to decide lock up or non lock up. Sounds like non lock up means less gas milage, more heat but more responsive versus better gas milage, less heat but sluggish on thd top end.
Yep actual stall of a TQ will depend on torque output of the engine... A big block will generally increase the stall over advertised, while a 6 cyl may not get within 200ft lbs of the advertised range... With lockup, a rumpy cam will likely cause some surge at lower speeds in O/D...
Exactly! My brother had a high reving 350 in his Chevelle with a TCI 3500 convertor and my GTO had a torque monster 455 with the same converter. Both cars weighed about the same and had 4.11s in the rear. His would flash to about 3,200 and mine to 4,400 when you mashed it. I always told him he needed a big block!
