1942 - 1947 Chevrolet Shop Manual



	7-19

	TRANSMISSION TRUCK-FOUR-SPEED TRANSMISSION CONSTRUCTION The four-speed transmission is a heavy-duty type of sturdy construction designed to give efficient service in every type of truck operation. The case is made of cast iron, accurately machined to give the proper alignment of the gears and their shafts. All gears are machined from drop forged steel gear blanks, heat treated for strength and long life. The shafts are machined from high grade steel, heat treated and ground to close limits. The clutch gear is supported by a heavy-duty ball bearing. The forward end of the main shaft is supported by a roller bearing inside the clutch gear, while the rear end receives its bearing from a ball bearing. Both ends of the countershaft run in heavy-duty roller bearings. Fig. 32 shows the sturdy construction of this transmission and the relative positions of all of the parts. This illustration shows the back end construction used with Hotchkiss drive design at the transmission. This back end construction differs slightly from that used with torque tube drive only in the shape of the rear bearing retainer and the spring loaded oil seal used with Hotchkiss drive around the hub of the universal joint front yoke. OPERATION Due to the simplicity of construction of the four-speed transmission, it is not necessary here to completely cover its operation.	TRANSMISSION SPECIFICATIONS Gear Ratios First Gear ................ 7.06 to 1 Second Gear ...............3.478 to 1 Third Gear ...............1.711 to 1 Fourth Gear ..............1 to 1 Reverse Gear ............ 6.98 to 1 Grease Capacity .......... 5-1/2 Pints NOTE—Although the three-speed transmission is regular production equipment in the 1/2, 3/4 and 3/4-ton special trucks, the removal and overhaul of the four-speed transmission in these trucks is covered in the following due to the fact that this transmission is frequently used in these models. The four-speed transmission, when used in the 1/2, 3/4 and 3/4-ton special trucks, is built for torque tube drive at the back end. Aside from this the assembly is identical with that used as regular production equipment in the 3/4-ton long Wheelbase panel and all 1-1/2-ton trucks including the Cab-Over-Engine model. REPAIR OPERATIONS REMOVAL OF TRANSMISSION FROM CHASSIS 1/2-TON TRUCK When removing a four-speed transmission from a 1/2-ton truck, it is necessary to remove the frame cross member so that the propeller shaft housing may be lowered. It is also necessary to back off the two capscrews that mount the brake main cylinder bracket to the side of the transmission case. It will then be possible to slide the transmission straight back on the guide pins, ALL 3/4-TON AND I-1/2-TON TRUCKS To remove a four-speed transmission from these trucks proceed as follows: 1. Remove the floor boards and disconnect the speedometer cable from the rear bearing retainer. Remove the hand brake lever from the transmission case. 2. Drain the lubricant from the transmission and remove the front propeller shaft assembly as explained under the Rear Axle Section of this Manual. 3. Remove the two top capscrews holding the transmission to the clutch housing and insert the two transmission guide pins in these holes. 4. Remove the flywheel underpan and remove the two lower transmission-to-clutch-housing capscrews. 5. Slide the transmission straight back on the guide pins until the clutch gear is free of the splines in the clutch disc. The guide pins in the

	Fig. 33—Four-Speed Transmission Gearshift Lever Positions
	The gearshift lever positions for the various gears are clearly shown in Fig. 33.