Page 454 of High Performance Parts for American V-Twins 2008 by S&S Cycle

drive train transmissions continued ­ s&s® all helical six-speed transmission pictured right s&s pn 56-1292 ­ flt owners will need this oil filler spacer kit that provides additional clearance between the s&s transmission trap door vehicle speed sensor and the engine oil filler neck gear ratios top gear of the s&s transmission is a 1:1 ratio and the transmission is supplied with a 34-tooth front pulley when used with a stock 70-tooth rear pulley the supplied 34-tooth pulley yields a final drive ratio that is equivalent to that of most overdrive six-speeds but there is a difference top gear in an overdrive transmission goes through a meshed pair of gears to achieve the higher gear ratio top gear in the s&s six-speed is 1:1 which means that the input shaft is simply locked to the output gear and there are no meshed gears involved at all the advantage less noise and less power lost as heat 56-1292 note when changing gear ratios or tire sizes it is essential that electronic speedometers be calibrated to read correctly s&s offers several products that can correct speedometer readings the s&s speedometer calibrator can compensate for a wide range of drive train modifications and has been around for years it is not as well known that the s&s ist ignition module also has a speedometer calibration function for 2004 and later carbureted models turndown ratio another important specification to consider is turndown ratio the s&s six-speed transmission has a turndown ratio of 3.882 which is higher than any stock or aftermarket v-twin transmission available first gear of the s&s transmission is lower than on a stock transmission so even with the 34-tooth front belt pulley the overall drive ratio in first gear is higher than stock see overall gear ratio chart on page 7-2 conditions and differing applications may require the use of different pulley sizes but the high turndown ratio of the s&s transmission allows such adjustments without sacrificing drivability or overall performance in simplest terms turndown ratio represents the range of adjustment to engine speed and final drive output offered by a particular transmission it is calculated by dividing the lowest internal gear ratio by the highest so turndown ratio in transmissions with a 1:1 top gear will always be the same as the ratio of first gear an overdrive transmission will have a turndown ratio that is higher than the ratio of first gear because the top gear ratio is less than 1:1 that s why it s important to consider turndown ratio when comparing the specifications of various transmissions a high turndown ratio allows a touring rider to gear high for the highway and still have a first gear low enough to pull a loaded bagger from a dead stop performance riders appreciate a high turndown ratio because it allows them to launch hard at the drag strip perhaps in second gear and still be able to ride in heavy traffic or at interstate speeds without difficulty complete transmissions s&s complete transmissions are built with bullet proof s&s transmission cases and are available in natural aluminum black powdercoat and polished finish all models come with a chrome top cover and a polished billet side cover s&s complete transmissions will fit 1991 99 harley-davidson® softail® models but can retrofit to 1986 90 models if a late clutch and a starter adapter are installed s&s low inertia 7-dog shifting rings are a good example of bigger is not always better although they are physically smaller than stock shifting dogs they are stronger and positively shift gears at much higher rpm due to their low mass and high aperture ratio continued on the next page 11-5 visit us at www.sscycle.com

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