Chapter 8 Manual Transmission Construction and Operation 167 Copyright by Goodheart-Willcox Co., Inc. Shift lever (2nd and 3rd) Shift lever (1st and rev) Shifter knob Locknut Gearshift lever Mounting pad Shifter support Gearshift lever assembly Chassis lubricant Swivel Trunnion Adjustment gage pin Shift rod (1st and reverse) Shift rod (2nd and 3rd) Chassis lubricant Gearshift lever Gearshift lever Insert Gearshift lever cover or boot Spring cover Floor pan Swivel ball Lever bushing Transmission Figure 8-17. The gearshift lever of an internal shift linkage is shown here. The gearshift pivots on an internal ball to move the shift linkage. Boots at the transmission and floor pan prevent the loss of lubricant and the entry of dirt and water. (Chrysler) in the vehicle floor pan. This hole is sealed by a flexible rubber boot, which keeps out dust and water while allow- ing gearshift lever movement. The gearshift lever assembly transfers gearshift lever movement to the shift rods. The shift rods operate the shift levers on the transmission case. Linkage parts for the external floor-shift linkage are attached with cotter pins through drilled holes in the shift rods. Washers and bushings are used at linkage pivot points to reduce wear, and the linkage can be adjusted by threaded swivels on the shift rods. Internal shift linkage Internal shift linkage is found only on transmissions with floor-mounted gearshift levers. In many instances, the gearshift lever extends down into the extension housing. The transmission and floor pan openings are sealed with rubber boots. Figure 8-17 is an example of such a gearshift lever. One common type of internal shift linkage employs a single shifter shaft, or shift rail. See Figure 8-18. The shift forks are positioned along the shifter shaft. When a gear is selected, the lower end of the gearshift lever moves into an offset lever at the end of the shifter shaft. Further movement of the gearshift lever causes the shifter shaft to move, along with the desired shift fork. The interlock plate locks out all gears except the one selected. Figure 8-16. In the external floor-shift linkage, a series of levers and rods transmit motion from the gearshift lever to the transmission. (General Motors)