14. Which of the following transmission components are splined to the main shaft in a standard, twin countershaft transmission? a. first speed gear b. sliding clutch c. countershaft gears d. idler gear

The correct answer is (a) first speed gear. In a standard, twin countershaft transmission the gears on the main (or layshaft) that provide drive ratios (especially the low‐end gear) are typically keyed or “splined” to the shaft so that they turn with it. The first speed gear is one such component—mounted via splines to the main shaft so it rotates in unison, even though its position is shifted (or “slid”) for engagement. The other components listed (the sliding clutch assembly, countershaft gears, and idler gear) are arranged differently: the sliding clutch isn’t splined to the main shaft; the countershaft gears are, by definition, mounted on the countershaft; and the idler gear is free–floating to facilitate proper gear meshing but is not splined to the main shaft. Thus, the only component among the options that is splined to the main shaft is the first speed gear.