Chapter 8 Manual Transmission Construction and Operation 169 Copyright by Goodheart-Willcox Co., Inc. Clutch housing Input shaft Transmission case Clutch fork Starter mounts here Throwout bearing Input shaft Front bearing retainer Transmission case For rear motor mount For speedometer cable assembly For rear seal Extension housing Vent Inspection cover Figure 8-22. This transmission case design makes the transmission easier to service. The gearsets can be more readily exposed. The gear train can then be easily disassembled and repaired. Several manufacturers use variations of this design. (Nissan) The transmission case is also the attaching point for the extension housing and external shift linkage. Figure 8-21 illustrates a typical transmission case. There are many vari- ations of this basic design, but the trans mission case always serves the same purpose. Transmission cases can be made of cast iron or aluminum. Many cases contain pressed-in bearings to support rotating shafts. Most manual transmissions have a lubricant fill plug and, sometimes, a drain plug. One modern version of the transmission case is shown in Figure 8-22. The case is made up of multiple pieces, including an adapter plate, or center support, which serves as the backside of the case. The adapter plate separates the transmission case and extension housing. The transmission shafts and gears are supported at the adapter plate and at the front and rear supports. This design makes the transmission easier to service. The opening in the front of the transmission case is covered by the front bearing retainer, sometimes called the front bearing cap, or front cover. See Figure 8-23. The front bearing retainer covers the transmission’s front bearing. The long hub of the retainer serves as the sliding surface for the clutch throwout bearing. To eliminate lubricant leaks, a gasket is installed between the bearing retainer and the case. Also, an oil seal is installed in the retainer, Figure 8-24. The front bearing retainer seal prevents oil leakage between the cover and the transmission input shaft. An access cover is commonly built into the top or side of the case. It allows access to the internal transmission parts for inspection or service. Depending on the design, Figure 8-20. The transmission case provides a mounting surface for the clutch housing. Some transmission cases and clutch housings, however, are a combined integral casting. (Chrysler) Figure 8-21. The transmission case supports, aligns, and serves as a mounting surface for the transmission components. The case also contains the transmission lubricant. (General Motors) Ball pin Front cover Front cover oil seal Slide ball bearing Gasket Drain plug Transmission case Filler plug Adapter plate Slide ball bearing Bearing retainer Rear extension housing Rear oil seal Dust cover Reverse amp switch Neutral switch