What does the STR affect,and how does it play into choosing a TC???Thanks to anyone that can help em understand

 

STR is how much torque multiplication you get
at high slip (like 3000RPM and not moving, at
launch). More STR makes more pavement thrust
and makes it "come on" over a narrower band
(you have to give slightly more pedal to move,
for the same rated stall speed, on a higher STR
converter but it takes less, beyond that, to get
the full torque multiplication).

STR is one way to make up for too-tall factory
gearing. It's also a good way to get your next set
of tires earlier

 

Everything jimmyblue said, the letters stand for Stall Torque Ratio, or torque multiplier.

The higher the STR, the more hookup problems you will have.

SteveC

 

the higher the STR the harder it hits off the line and slight lose of top end power

 

So if you have a 2.5 str, like me, and you have around 330 tq, then at launch at the stall speed you put down 825 tq? Is that the proper undersanding

 

That's about it, however it drops off dramatically after launch. It would not show on the dyno.

SteveC

 

That amount of torque though would only be applied though when and if you braked the car to launch at that rpm, like 3200-3400 in my case?

 

You see it on the dyno as absurdly high RWT values,
"torque spikes", if you start at low enough RPM unlocked
or downshift at the start of the pull.

As the input shaft RPM rises, the coupling goes toward
1:1 and conversely, the improved coupling works more
to hold down the engine RPM until the output shaft
catches up.

 

I agree totally, I have had torque spikes on the dyno jet as high as 370 between the first and second shifts

SteveC