Why 15-Speed Drivers Didn’t Shift Through All 15 Gears.

An Eaton Fuller 15-speed didn't work the way the number on the transmission suggested. Run one from deep reduction toward top gear and three of the listed ratios could put the driveline almost exactly where another gear already had. That overlap was not a design mistake. Deep reduction gave a loaded truck extremely low starting ratios when grades, poor footing or sheer weight made clutch slip expensive. On the later 14-915 and 16-915, the ratio spacing explains why drivers did not simply march through fifteen separate gears, and why the real skill was knowing when to get out of deep reduction. The Eaton Fuller Roadranger 15-speed also behaved very differently from the familiar 13-speed. Its button worked at the bottom of the transmission rather than the top, its air system tied deep reduction to low range, and leaving deep could require moving the stick to a lower-numbered position while actually upshifting the truck. The ratios, operating manuals and air-system logic show how experienced drivers really used these old 15-speed transmissions. --------- We do not fully own the material compiled in this video. It belongs to individuals or organizations that deserve respect and consideration. This video was created under the Fair Use Law Section 107 of the U.S. Copyright Act of 1976. "Fair use" is allowed for purposes such as criticism, comment, news reporting, teaching, and research. It is transformative in nature, uses no more of the original than necessary, and has no negative effect on the market for the original work. #vintageamericanmachines #vintageengines