1942 - 1947 Chevrolet Shop Manual



	*7-13*

	5. Assemble the transmission cover and gasket to the case, using the two special capscrews at the front. 6. Place the gearshift lever housing over the shift lever; install the shift lever spring and ball seat in the retainer. 7. Assemble the retainer and gasket to the transmission cover with the four capscrews, drawing the screws down evenly to prevent the shift lever spring from exerting a strain on the die-cast retainer, or by using two longer capscrews in opposite holes to aid in compressing the spring enough to start the short screws in place; then remove the two long screws and replace them with the other two regular screws. 8. Check the operation of the transmission by shifting into all gears. VACUUM GEARSHIFT (Passenger Cars) The Vacuum Gearshift operates essentially the same as on previous models. In this system both physical and vacuum effort are combined to effect transmission gear changes. The majority of the effort, however, is exerted automatically by the engine vacuum when the engine is running. The transmission gears may be shifted manually without the aid of the vacuum effort, which is also the case when the engine is not running. VACUUM CYLINDER When the gearshift lever is in neutral position it will be noted that the valve is in a position that admits atmospheric pressure to both sides of the	piston. When the gearshift lever is moved forward as when shifting into either reverse or second speeds, the inner sleeve valve is moved forward and vacuum from the engine is applied to the forward side of the piston, and outside air passes to the rear side, Fig. 22. This causes the piston to move forward in the cylinder. When the gearshift lever is moved backward, as when shifting into either low or high speeds, the inner sleeve valve is moved backward in the piston rod. This uncovers the rear port in the piston rod and applies the engine vacuum to the rear of the piston at the same time the forward port is opened to the outside air and the piston is moved backward, Fig. 23.


		Fig. 23—Vacuum Cylinder in Position when Shifting into Low or High Speeds
		GEARSHIFTING In the following explanation of the action of the shifting mechanism when a change of gears is desired, we will assume a definite gear change for an example. When a shift is to be made from neutral into second gear, the initial forward movement of the gearshift lever causes the gearshift control rod to move forward and, in so doing, pulls the vacuum cylinder valve rod forward, admitting vacuum to the forward side of the piston and outside air to the rear as shown in Fig. 22. This is accomplished without moving the transmission operating lever because the control rod clevis pin is a loose fit in the transmission operating lever, the gearshift control rod links, and the sleeve valve link which is a loose fit on the vacuum cylinder piston rod yoke pin.
	Fig. 22—Vacuum Cylinder in Position when Shifting into Reverse or Second Speeds