Automatic Transmission Performance - Auto Tech

So if you are racing with a working torque converter (instead of a dummy converter that provides a direct mechanical linkage) you should definitely also run a transmission oil cooler. This is because the cooler you keep your transmission fluid, as well as the components in the transmission, the better and longer it is going to work. And racing definitely produces much more heat than the street service the transmission was originally designed for. So if your car isn't already equipped with a cooler, you can actually save money in the long run by investing in one.

Miller recommends buying at least a medium-size cooler. "About a 20,000 to 22,000 gvw-rated cooler is normally fine," he says. "Stay away from the one-way flow coolers because if you somehow mess up and get it hooked up backwards, that can cause problems with the transmission. And those one-way style coolers can plug up. Say you have a transmission that goes out, and it gets a bunch of contaminants in the cooler. The one-way cooler will clog up and the only thing you can do with it then is throw it away."

Avoid Fluid Failures
Speaking of keeping your automatic transmission fluid clean, the fluid you choose can also dramatically affect performance as well as the lifespan of your transmission. "When it comes to fluids, just make sure you run a good quality ATF. It doesn't have to be a pure synthetic, but just make sure it's better than the dollar-a-quart stuff you can buy at the local parts store," Miller says. "You should also plan to change your fluid every 200 to 250 laps.

"And you should also know that not all fluids are the same. I can't speak for other manufacturer's ATF fluids, but I can speak about our two different types as an example. Our Max Shift STF is our top-of-the line synthetic fluid. But then we have Max Shift RTF. That's a Dextron 3/Mercon-based fluid that has a moly additive in it. What that does is the moly actually does bond to the metal parts better. And with heat buildup, it doesn't break down. It stays bonded to the planetary gears and washers and the sealing rings and things like that to cut down on wear. By using a fluid like that it will actually help the transmission run a little cooler."

Miller also recommends making sure you run the correct dipstick for your transmission. Many racers will plug the hole for the dipstick tube and fill the transmission case with fluid. But overfilling the transmission can lead to fluid blowing out the vent or leaks at the seals. And the last thing you want is to get black flagged because you are blowing oil onto the track.

Find The Right Converter
One of the biggest advantages you can find on the racetrack is by using the best torque converter for your needs. You might think a torque converter with a higher stall speed (the rpm level at which the transmission reaches maximum lockup) will give you an advantage because it should allow the engine to get up into a higher rpm range before kicking in, but Miller says that really isn't the case.

"If you are a drag racer, you want a converter with a fairly high stall speed, but in stock car racing, that isn't helpful," he says. "A higher stall in circle track racing means more slippage. And more slippage means less power is getting to the ground. The other issue is a high-stall converter can actually help cause things like wheelspin. Because it doesn't kick in until the engine has reached a high rpm level, and when it does kick in, it kicks in real hard and the driver can have an issue coming out of the turns.

"So you don't want to put a converter for a drag-race car or a street application into your racecar. We've designed converters specifically for circle track racing. They are very low stall and have good torque multiplication, so they lock up quickly and there is very little power wasted. That's the key so when the car comes out of the turns and you get on the throttle, you don't have that slippage in the converter. You are getting the power to the ground.