Keeping Driveline Modifications Viable

Between the price of gasoline and diesel fuel and the environmentalists who expect all internal combustion engines to emit nothing other than flowers and perfume from the exhaust pipe, engine modifications have taken a hit. Fewer automobile enthusiasts seem to be making major, hard-core upgrades to their gasoline and diesel engines. That's really too bad because most engine modifications that increase horsepower usually also increase the efficiency of the engine, and therefore, once the novelty of the added performance has worn off and the driver settles back into a normal driving mode, the fuel economy delivered by the modified engine increases.

Most new vehicles, with the exception of some performance vehicles, are sold with automatic transmissions and/or automatic transaxles. For decades, there used to be a fuel economy penalty for having an automatic transmission. Typically, there was an EPA rating of 3 to 4 fewer miles per gallon with an automatic transmission. Today, that isn't always so. GM's old PowerGlide transmissions and Ford's Ford-O-Matics had just two speeds forward. The combination of lots of torque and a torque converter meant that two speeds were enough, but there was a significant fuel economy penalty. But modern vehicles equipped with automatic transmissions usually have four or five speeds forward, and some sophisticated new automatic transmissions, such as those found in the new BMW and Lexus sedans, have seven or even eight speeds forward.


Today, big diesel engines in full-size pickup car parts have huge 13-inch wet disc lock up clutches (they are located inside the torque converter itself) and some vehicles have smaller, multi-disc wet clutch setups.

According to Bob Ritzman, director of motorsports and customer service at B&M Racing and Performance Products, "Sales of torque converters are down somewhat. One reason for this is that the manufacturers are matching the torque converters directly to the cars." It used to be that automatic transmission choices were limited and that meant the choice of torque converters was limited too. Since there were only TH350 and TH400 from GM, C-4 and C-6 from Ford and the TorqueFlite A727 from Chrysler during the muscle car era, it was easy for a manufacturer to build and for retailers to stock high-performance torque converters.

"Recalibrating the automatic transmission computer has in some cases replaced the old valve body kit modifications. You can achieve pretty much the same result without getting your hands dirty. You can use a black box to talk to the transmission computer to recalibrate the shift characteristics of the automatic transmission. B&M still manufactures valve body kits and we are currently developing a new synthetic automatic transmission fluid that will meet the auto manufacturer's specifications."

"Modern automatic transmissions have more gears and they also have lock up torque converters that make them more efficient than ever," Ritzman continues. "It's not uncommon now to have many gears and to have EPA fuel economy estimates equal or sometimes even better for the automatic transmission vehicles.

"Recalibrating the automatic transmission computer has in some cases replaced the old valve body kit modifications. You can achieve pretty much the same result without getting your hands dirty. You can use a black box to talk to the transmission computer to recalibrate the shift characteristics of the automatic transmission. B&M still manufactures valve body kits and we are currently developing a new synthetic automatic transmission fluid that will meet the auto manufacturer's specifications."