The NV5600 uses three housings to hold its internal components. At the front of the transmission, the all-aluminum clutch housing (Fig 7) mates to the engine block and includes the front bearing bulkhead. The clutch housing is integral to the gearbox, and cannot be separated form the transmission while in the vehicle.

The durable, cast iron main case is the largest and heaviest of the three housings. It covers the bulk of the geartrain. At the rear of the NV5600 is the extension housing on 2WD applications or the adapter housing on 4WD vehicles. It too is made of cast iron.

Inside these housings is constant mesh, helical gearing that is designed for at least 250,000 miles of useful life. The NV5600 uses long-life, tapered roller bearings (Fig 8) to support the input shaft, the output shaft, and the countershaft. 

Steel-caged needle bearings are used with all speed gears, which minimizes friction and helps reduce shift effort. These needle bearings are also put to use under the reverse idler gear.

The NV5600 transmission employs a pretty unique shift system that is not only reliable and durable, but also produces a smooth, crisp shift feel that was previously unknown in this segment of the truck market. A big reason for this level of shift quality is the use of synchronizers for all gears including reverse (Fig 9). 

The synchros for 1-2, 5-6, and revers shifts are located on the upper shaft, while the 3-4 synchronizer is mounted on the countershaft. Positioning the synchronizer on the countershaft helps reduce gear rattle.

Other synchronizers are all a single cone design.

The innovative, multirail shift mechanism is operated by a single shift finger and interlock bushing. The four cast aluminum shift forks (Fig 11) that perform the gear changes have 180 degree contact at the synchronizer sleeve. The use of a crossover cam provides a detent for the reverse shift gate, and gives a better sense of where each shift gate is located.

The NV5600 has a lifetime lubrication system, which further bolsters its durability while reducing maintenance needs. All speed gears have forged oil slots (Fig 12) to facilitate the lubrication of the gears and bearings. Oil guides are used in the NV5600 to ensure that the pocket bearing between the input and output shafts stays well lubricated, which is critical to smooth operation.