THE SHOP

Performance & Hotrod Business - July '15

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July 2015 n Performance & Hotrod Business n 43 so we can cover the widest range possible." American Powertrain already supplied flywheels and related components for such out-of-the-mainstream installations as Buick, Oldsmobile, and AMC. "Many other companies have stopped making these parts because they are looking for the low-hanging fruit." Fredrick remarked. "But if a customer wants to install a Tremec behind an Olds 455, they need a flywheel for the job. So for this job and others we send every nut, bold and fitting, so you never need to go pounding on the parts store door on Saturday afternoon." Diminishing Returns? And yet, while manual-shift customers of all allegiances have eagerly adopted six- gear boxes, they've shown little interest (so far) in shifting through eight or nine ratios. " With a manual transmission," Fredrick observes, "there's a law of dimin- ishing returns. Six gears seem nearly ideal for low- and mid-range performance with great highway cruising and fuel mileage. I think the idea of clutching eight or nine times to reach the final gear would turn most people away. And keep in mind that manual transmissions are much more efficient at getting the power to the rear wheels, and can take advantage of that feature by spreading the gear ratios wider. Eight and nine-speed automatics are just making up for their inherent inefficiencies. "And here's an additional thought: Because automatic transmissions use sun gears, they are more compact in length. Adding gears to a manual transmission increases its length, weight, and inter- nal drag, all enemies of proper fit and high-performance." Another popular OE feature—sequen- tial shifting controlled by steering-wheel paddles—has received at best mixed reviews in the hot rod and muscle car mar- kets. According to Winstead, paddle-shift setups are "popular for street-and-strip cars, and autocross applications." But Strange remains skeptical. "The paddle-shift option has always been something of a novelty in the auto- matic-transmission market. Several types are available, but really only one or two function in a way most performance enthusiasts would be happy with. The main issue is the time between the input from the paddle and the response from the transmission." Dual-clutch manuals offer better response, "but are priced so far above any traditional manual transmission that very few customers would consider one for a project car." Gear-Jammin' Strong as the new transmissions are, hot rodders like horsepower, and if they build enough of it, then not only the transmis- sion but other driveline components will require upgrades as well. "As horsepower is increasingly easy to make," says Strange, "our customers require increasingly stronger transmis- sions. At one time we offered two levels of upgrade, which we called Level 4 and Level 5. More recently we've added Levels 6 through 10." When asked about inherent weak- nesses, Strange points first to the factory flexplate. "Factory flexplates are not designed for high-horsepower applications, and can crack or even break under increased stress. The next step is the torque converter; then the driveshaft and slip yoke. A yoke that's not on par with the transmission can twist, causing issues with the transmission out- put shaft and tail housing bushing. And a broken driveshaft can jam the yoke into the transmission." Winstead agrees that automatic trans- mission customers should always beef up their torque converter to match the torque-resistant toughness of their new planetary gear set. "And the transmission cooler needs to be upgraded, too—or at least flushed—at the same time." TCI calls its entry-level performance automatic the Street Rodder. "It works nicely for customers who want smoother shifting and less than 500 horsepower," says Winstead. "The Street Fighter is our next step up, featuring upgraded internal components and run- ning higher line pressures for firmer shifts than with our Street Rodder." TCI's top-level transmission—at least the top-level unit still capable of automatic shifting—is the Super Street Fighter, "with more clutches than the Street Fighter and, in some applications, billet input shafts. And line pressure is higher yet." Shifting Over Old muscle cars that came with a per- formance four-speed manual still require "simple things," says Frederick, "such as speedometer cables, reverse-light wiring, a pilot bearing, a suitable crossmember and a high-quality driveshaft." Customers making the ultimate trans- mission conversion—from factory auto- matic to high-capacity manual—"will need new pedals, obviously, but also a flywheel, clutch and bellhousing, plus a mechanical or hydraulic clutch linkage," Fredrick adds. "But again, since American Powertrain makes all of these parts, and offers them as systems, we are able to provide customers with just what they need—without selling them parts that will go unused, or shorting them on the parts they need to complete their installation." John F. Katz is a freelance automotive journalist and historian. He is a regular con- tributor to Performance & Hotrod Business as well as other automotive industry pub- lications. He lives and works in south-central Pennsylvania.

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