Just what exactly does a performance torque converter do. How does it change the way the car drives and reacts compared to stock or as I have done the 2.73 to 3.42 swap?

 

A high stall T/C allows your engine to instantly rev up higher in the power band where your engine is making alot more power when you go WOT. A T/C like the Yank SS3600 stalls at 3600 RPM the stock T/C stalls at only 1600 RPM. Your engine makes alot more HP at 3600 RPM than it does at just 1600 RPM. A high stall T/C will also get rid of the dead spots in acceleration like when you go WOT at 35-40 MPH. Gears alone will not get rid of the dead spots. A high stall T/C also will give you much higher shift extentions than the stock T/C.

In general you will need a little more RPM get moving when you pull off from a standstill with a high stall T/C. How much extra RPM that is required depends on the stall speed & the design of the converter.
Some of the mild converters (2400-2800 stall) feel like stock if you have 3.42 or better gears.

 

This guy is correct with some aspects of the torque converter. But keep in mind GM built your drive train to preserve durability and drivability. Installing a 3600 TC may cause severe stress on your transmission and shorten the life of your drivetrain. I would recommend a transmission rebuild if you plan to install a TC above 2400 and have heavy launches. Just my opinion.

 

I put over 30,000 miles on the bone-stock transmission in my 1999 Camaro SS with a Yank ST3500 installed and have around 20,000 miles on the bone-stock tranny in my 2000 Corvette with first a Yank 3000 and now, since a few thousand miles ago, a Yank SY3500.

Will high-stall torque converters shorten the life of your tranny and drivetrain. Yes, most likely they will, just like making more horsepower will, and just like driving aggressively will. Is it a big worry or is failure imminent as soon as the high-stall converter is installed? Not hardly.

Do want you want to do, have fun, and leave the worrying to the feint of heart.

Regarding your original question about what a performance torque converter does............

A high-stall torque converter increases performance in a couple of ways. The first is the obvious one in that it helps you off the line via its higher stall speed and increased torque. The other big advantage provided is what's called “shift extension.” With a high-stall converter when your transmission shifts at WOT, instead of the engine speed dropping down to 3000-3500 rpm, it will stay at 4000-5000+ rpm (depending on the converter) and you'll be right back up to redline again for your next shift. This results in your motor staying in the meat of its power band for the whole run and that translates into improved ETs. This “shift extension” factor will help even if you never visit a drag strip, as it will eliminate the “dead spot” that stock/lower-stall converter cars suffer from. Now when you accelerate and your transmission kicks down into passing gear, instead of your engine having to build up speed from the 3000 rpm range, you'll be starting at that higher engine speed. This translates into better acceleration, better performance, and safer passing.

 

I agree with most everything that has been said. Anytime you put in a
high stall converter you NEED to also install a trans. cooler. A high stall
will cause higher trans. temps. and thus shorten the life of the tranny.

 

I was a person very worried about losing my stock drivabilty, so when I replaced my 2.73 gears to 3.42 gears people told me to do the converter also but I was too afraid it would make my car difficult to drive around town. I did not change it till one year later. I was SO wrong! I wish I would have changed out the converter first. The stick guys hate it when you tell them you have a high stall converter because they know they have to get a perfect shift to beat you. I feel by changing the converter you level the playing field. I highly recomend changing it out. Go to a car club meeting in your area and go for a ride in a car with one and it will easy your worries.
Oh, also do the trans cooler. Flp explained to me the main reason a4's fail is the heat. The clutch packs get too hot and start to slip. So do the cooler and you will be fine.

 

What you say above is entirely correct for most every vehicle in existence, but in regard to the C5, I've found this not to be the case. I attribute it to the fact that the transmission is isolated from engine heat and has better air circulation being positioned in the rear, but whatever the reason, my ATF temps (which I've diligently monitored for months) haven't gone up a bit. I first had a Yank 3000 and now a Super Yank 3500 converter in my car and my tranny fluid temps average in the 180's. On rare occasions, maybe once or twice a year, in very hot temps while in heavy traffic, the temps may rise to or slightly exceed 200 F.

 

It took me 4 hours to drive 150 miles home from the track yesterday. With a Yank 4400 stall and 4.10's my tranny temps didn't go above 210. If you lower your fan turn on temps, you don't need an external trans cooler unless you run on a road course.

 

This is a very informative thread. I have learned a lot from reading this. Thank you to everyone that posted and the thread starter.