Transfer Case Exchange

Rok Trac

Rock Trac
Chain Driven


Most transfer cases can be repaired or rebuilt but, if if there is case and gear damage it may be more cost effective to exchange the unit.

Most present-day light duty transfer cases are chain-driven with alluminum cases, weigh less, and operate quieter than the gear-driven units.

Generally, transfer Case repairs consist of bearings, clutch plates, seals, gaskets, shift forks, fork pads and a chain . Gear damage such as planetaries, drive or driven sprokets, hubs, etc add to the cost of the repairs.


THE BASICS

The transfer case splits the torque coming from the transmission and delivers it to the front and rear axles. Most transfer cases designed for off-road use are able to mechanically lock the front hubs so that each axle gets an equal amount of torque. Depending on the age and design of your transfer case, torque is delivered to the front output shaft either through a set of gears or via a chain. Most present-day Transfer-cases are chain-driven and are quieter than gears. Hard-core four-wheelers tend to prefer the old-school gear-driven cases because they can withstand greater amounts of torque without breaking.

PART-TIME OR FULL-TIME

NP241C

NP 241C

It used to be that almost all transfer cases fell into one of two categories: part-time or full-time. A part-time transfer case is one that can shift between two- and four-wheel drive, allowing the driver to select the mode that best suits road conditions. Wear on the front-drive components is reduced with a part-time system, since they’re not always engaged, and fuel economy is generally better for the same reason. A full-time case is permanently in four-wheel drive, so no action on the driver’s part is required to engage the system. In order to use a full-time transfer case on hard-packed surfaces without binding the driveline, the case must be built to allow driveline slip between the front and rear wheels. Some (like the NP203) contain differential gears inside the case, while others use some sort of clutch or viscous coupling between the T-case and the front driveshaft. In both cases, there is typically a means to lock the slipping mechanism for a true 50/50 torque split when conditions warrant.

NVG246 AUTOTRAC

Rok Trac

NVG246 AUTOTRAC

The latest developments in transfer case technology include hybrids that combine full-time and part-time functions in one unit. Shown here is GM’s NVG246, otherwise known as the Autotrac system. It uses a number of sensors and its own computer to direct torque when in full-time mode, plus it has the traditional part-time 4-High and 4-Low modes as well. The Autotrac system is found on fullsize GM trucks and has made its way to the midsize TrailBlazer and Envoy SUVs.