162 Manual Drive Trains and Axles Copyright by Goodheart-Willcox Co., Inc. The size of the individual gears on the cluster increases with each drop in gear ratio. For example, second gear has a smaller ratio than first gear, and it is larger in size than first gear. Third gear has a smaller ratio than second gear, and it is larger than second gear. Countershaft gear front thrust washer (plastic) Countershaft gear Countershaft gear rear thrust washer (metal) Countershaft needle bearing retainer (2) Countershaft needle bearing (50) Countershaft roll pin Countershaft Case Input shaft gear Input shaft from clutch disc Cluster or countershaft gears Reverse idler gear Extension housing Speedometer drive gear Output shaft to drive shaft Shift lever Shift rail Output shaft gears Shift fork Gear synchronizer Figure 8-7. This cutaway points out the various parts of a modern 5-speed manual transmission with overdrive. Notice how the main drive gear fits into the transmission case and meshes with the countershaft gear. (Ford) Figure 8-6. Exploded view shows the parts of the countershaft gear assembly. This shaft is locked in place by countershaft roll pin. Thrust washers control endplay in the countershaft gear. The countershaft gear rides on needle bearings. (Chrysler) In most designs, the countershaft gear rotates on a countershaft that is stationary. Needle bearings are used between the cluster gear and shaft to reduce wear. Needle bearings may be loose, or they may be caged. Some designs incorporate caged needle bearings because they are easier to work with. The bearings do not fall all over the bench during disassembly, and installing the bearings is also much easier. Thrust washers placed between the ends of the assembly and the transmission case control endplay, or back-and-forth movement, of the countershaft gear. In some transmissions, the countershaft gear is supported, and endplay is controlled through the use of tapered roller bearings. Figure 8-8 shows tapered roller bearings used on a countershaft gear. Some gears are in constant mesh with the countershaft gear: one is the main drive gear and the other is the reverse idler gear. In modern transmissions, all forward gears of the countershaft are in constant mesh with the mainshaft gears, which are free to rotate. These are sometimes referred to as constant-mesh transmissions. Reverse gear may be the constant-mesh type, or it may be the type that slides in and out of engagement. In some early constant-mesh transmis- sions, both first and reverse used sliding gears. Mainshaft gears The output shaft contains the gears that provide for- ward speeds and reverse. Mainshaft gears mount over the transmission output shaft. See the mainshaft gear assembly