Automatic Transmission Performance - Auto Tech

Stock car racing and automatic transmissions aren't two things that you normally think of going together. But you can find automatic transmissions at racetracks across the country, and they are helping to provide some pretty good competition.

You will mostly find automatics in Street Stock-level racing classes that demand most of the driveline components in the car be stock or stock-replacement. Of course, these are also some of the most popular classes out there because they are aimed at keeping the costs contained and the technology simple so that just about anyone can try their hand at racing. But just because it may be an entry-level class doesn't mean that you can be successful running a bone-stock transmission in a season of racing action. That's a recipe that will likely leave you frustrated with multiple breakdowns or various nagging problems that will have you spending more time with your hands gripping wrenches than a steering wheel.

Instead, we went to Scott Miller of TCI to get some tips from the experts on how to race successfully-and inexpensively-with an automatic transmission. TCI is one of the top builders of performance automatic transmissions and transmission upgrade kits in the country. And while many performance trans builders are still geared solely toward the bracket drag racing market, TCI has noticed the growing trend of automatics in stock car racing and has specific technologies just for the stock car racers.

Try The Turbo
When it comes to stock car racing with an automatic transmission, the Turbo 350, found mostly in Chevrolets, is by far the most popular option. Often, it's also one of the few allowed in the rulebook. Miller says one of the reasons for its popularity is that you can safely run it in Second gear and get the engine into a higher rpm range.

"One thing about running the Turbo 350 is everybody will have an opinion on how to get it to run on the racetrack," Miller adds. "You don't really want to use a stock configuration for shifting the valve body. Some people will tell you not to hook the vacuum to it. Others will tell you not to hook up the kickdown linkage and it will work fine. Well, it will work, but it will also burn up a lot more quickly in racing conditions because that's not the way it was designed to be used. The best answer is to put a full manual valve body on the transmission and then once you are racing, change the fluid and filter about every couple hundred laps. Adding a mechanical valve body isn't hard. You can even do it while the transmission is still in the car. And as long as you have a good transmission when you started out, you should be fine."

Make Your Life A Little Easier
This tip won't exactly make you any faster on the racetrack, but it will definitely make your life a little easier. Most transmissions don't come from the factory with a drain hole in the oil pan. Working on the transmission or completely draining the fluid requires removing the oil pan-and the oil always spills out the sides and gets everywhere, including on you. This isn't as big a deal in a street car because the transmission fluid isn't changed that often. But if you are going to change the trans fluid in your racecar after every 200 laps, this can quickly become a very big hassle. Spend a little money on an aftermarket oil pan for your transmission that includes a drain plug. It will make regular maintenance a lot easier.

Keep It Cool
One of the problems that come with racing an automatic transmission with a working torque converter is that there isn't a direct mechanical linkage between the engine's crankshaft and the driveshaft. The transmission uses a fluid coupling which allows the car to idle with the transmission in gear. Using a performance torque converter instead of an inefficient stock converter will cut down a lot on slippage, but the fluid coupling will still produce heat.