Selec-Trac on 85 Wagoneer.

[drakan1908]

From Wikipedia

Selec-Trac was first introduced in the full-size Jeeps (SJ) in 1983 using the New Process NP229 transfer case. This system has the same settings as Command-Trac but instead of locking the front and rear drive shafts together in the "4Hi" setting the drive shafts were coupled together using a viscous-type coupler that works the same way as a viscous limited-slip differential does; which allowed the vehicle to be driven in "4Hi" on dry pavement. It was used from 1983 to 1991 in some applications.

The AMC Eagle used the NP119 transfer case in 1980, a strictly full-time all wheel drive model. From 1981 to 1988, a similar system was employed, dubbed "Select-Drive", which allowed the vehicle to switch from all wheel drive to 2WD using the NP129 model transfer case. The NP129 contained a viscous coupling around an open differential for added traction in slippery conditions. The NP128 has also been found equipped in select model years, which does not feature a viscous coupling.

The NP228 Selec-Trac transfer case is closely related to the NP229. The only difference is that the NP228 does not have a viscous-type limited-slip coupling. It was used briefly in 1986.

The NP242 Selec-Trac transfer case debuted with the compact Jeep Cherokee in 1984. It is a more common feature in the upscale version Jeep Wagoneer (XJ), and Dodge Durango models (1998–2003). It has a shift-on-the-fly transfer-case like Command-Trac but unlike it, Selec-Trac offers full-time all wheel drive in addition to the part-time 4WD of Command-Trac. Full-Time all wheel drive has the ability for the front and rear axles to rotate at different speeds, making driving on dry and wet surfaces possible year-round without shifting back to 2WD again. It still has the ability to lock the front and rear axles.

Other Jeep vehicles used Selec-Trac, for example, the Jeep Grand Cherokee, before being discontinued on that platform in favor of the electronically controlled Quadra-Drive II four-wheel drive system in 2005.






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