Manual transmissions are an icon of the automobile hobby. The ability to operate a car with three pedals sets an individual apart from the mass of drivers who just see cars as point-a-to-point-b transportation. “Driving a stick” lends a certain air of mystery and adventure to a car owner.
Still, how many devotees of the clutch pedal can tell fact from fiction when it comes to the innards of their beloved gearbox? Most of us don’t know a lot more than the number of forward speeds and how many of them are synchronized. It doesn’t need to be that way. The selection, installation, and maintenance of what was once called the standard-shift transmission can be quite straightforward.
From a three-on-the-tree to the seven-speed in a C7 Corvette, all manual transmissions have certain points of commonality. The muscle-car four-speeds of the ’60s and ’70s are likely the most familiar to Hemmings readers, but five-speeds like the Borg-Warner T-5 have been with us nearly 40 years. Even the beloved T-56 six-speed came on the scene in 1992, with the Dodge Viper. That’s a lot of accumulated knowledge. To get the latest information for gearjammers, we consulted with TREMEC dealer Silver Sport Transmissions. Below are five things to consider when contemplating a manual transmission in your ride.
1. Overdrive in Moderation
Historically, a transmission’s top gear transmitted power from the engine in a 1:1 ratio (“direct drive”) where one turn of the engine causes one turn of the driveshaft. Starting in the Seventies and Eighties, however, manual transmissions adopted overdriven top gears, meaning the engine can be turning slower than the driveshaft. When selecting an overdrive ratio, keep in mind that the lower the number, the more overdrive. On a TXK five-speed trans (shown above), the buyer has a choice of 0.81:1, 0.72:1, and 0.68:1, which offer 19-, 28-, and 32-percent overdrive, respectively. Beware of falling into the “more is better” trap, however. As with camshafts and carburetors, too much overdrive will work to your disadvantage. Unless you have an engine built for it, matched to the proper rear-end ratio, you may find yourself lugging the engine in overdrive
2. Keep things in Sync
Synchronizer rings and cones smooth the transition from one gear to another, so that you only have to press in the clutch once per shift. They may date back to the 1930s, but they’re not limited to the technology of that era. While traditional brass construction still persists for most applications, Silver Sport’s experts note that they wear faster than some options now available. Worn synchros lose their grip and exhibit crunching where crisp shifts used to be the norm. “If you plan on high-rpm shifts or if you’d like to extend the life of your transmission before it needs a rebuild, carbon-lined synchronizers are the way to go,” said Silver Sport’s Misty McComas. Carbon linings come in both partial and full varieties. With partial (shown above), only the blocker ring or cone is lined, but with full, the whole synchronizer is lined. The latter is recommended for situations where more grip is desired. Even if you’re not power shifting, a harder-wearing consumable means more fun time versus maintenance.