Manual Transmission/Transaxle: Description and Operation

NV3550 MANUAL TRANSMISSION

DESCRIPTION
The NV3550 (available for both 2.4 & 3.7L engines) is a medium-duty, 5-speed, constant mesh, fully synchronized manual transmission. The transmission is available in two and four-wheel drive configurations.

The gear case consists of two aluminum housings and a removable clutch housing. The clutch housing is not an integral part of the transmission.

Roller bearings and needle bearings are used in the transmission. The transmission gears all rotate on caged type needle bearings. Roller bearings are used to support the input, output and counter shafts.

The transmission has a single shaft shift mechanism with three shift forks all mounted on the shaft. The shaft is supported in the front and rear housings by bushings and one linear ball bearing. Internal shift components consist of the forks, shaft, shift lever socket and detent components.

The drain plug is located in the bottom of the transmission and fill plug is on the left side.

OPERATION
The driver selects a particular gear by moving the shift lever to the desired gear position. This movement moves the internal transmission shift components to begin the shift sequence. As the shift lever moves the selected shift rail, the shift fork attached to that rail begins to move.

The fork is positioned in a groove in the outer circumference of the synchronizer sleeve. As the shift fork moves the synchronizer sleeve, the synchronizer begins to speed-up or slow down the selected gear (depending on whether we are up-shifting or down-shifting).

The synchronizer does this by having the synchronizer hub splined to the mainshaft, or the countershaft in some cases, and moving the blocker ring into contact with the gear's friction cone. As the blocker ring and friction cone come together, the gear speed is brought up or down to the speed of the synchronizer. As the two speeds match, the splines on the inside of the synchronizer sleeve become aligned with the teeth on the blocker ring and the friction cone and eventually will slide over the teeth, locking the gear to the mainshaft, or countershaft, through the synchronizer.