Sunday, March 9, 2014
Information on a NP229 Transfer Case
The NP229 transfer case was manufactured by the New Process Gear Division of Chrysler, also known as the New Venture Gear Company. The unit was used by Jeep from 1982 through 1991 as their "Selec-Trac" option.
NP229 Basics
The NP229 is a part-time unit with an aluminum case. It is chain-driven and features an offset output. As a part-time 4WD case, it should only be used in 4WD mode when on a slippery surface. This is because the front and rear axles are locked together, and binding may occur on regular surfaces, causing damage to the driveline.
NP229 Applications
The NP229 transfer case was installed in XJ Jeep Cherokees and XJ Jeep Wagoneers from 1984 to 1987. The case was also used in full-size Jeeps as the "Selec-Trac" option from 1982 to 1991.
Unique Feature
The NP229 used vacuum and mechanical shift with viscous coupling. A vacuum-actuated switch was installed on the center console or dash to change between 2WD and 4WD. This switch was routed directly to the transfer case. Early models featured a lock-out mechanism to prevent on-the-fly switching, which would result in severe damage to the unit.
