From JeepTech and JeepTech Publishing LLC, the Jeep knowledge base.
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These articles detail the transfer cases that were offered from the factory in various Jeep models. Transfer cases are arranged by the most recently introduced first.
NOTE: Other auto manufacturers use New Venture (was New Process) cases and they are generally designated with a letter to differentiate them. IE: J for Jeep after the part number.
In order to narrow the scope of work to put these articles together, they were originally written to cover only the transfer cases found in CJs, YJs, and TJs. The scope is being expanded to cover transfer cases used in all Jeep models.
NP-242: The NP242, (also known as the NV242 when it became 23 spline in '91), is a full-time transfer case used in Cherokees (XJ) and Grand Cherokees (ZJ).
NP-231: Since 1988, the NP231 has been the "Command Trac" transfer case used in Cherokees (XJ), Comanches (MJ), and Wranglers (YJ). It has been the "Command Trac" transfer case in the Grand Cherokee (ZJ) since its introduction in 1993. The new Wrangler (TJ) continues to use the NP231 (except Rubicon which uses a NV241-OR Trac Loc with 4:1 low range).
NP-207: The NP207 was used in the first year of Wranglers in 1987. It was used in Cherokees (XJ) until from '84-'87 and replaced with the NP231.
NP-208: The NP208J was an option used in 1980 to 1983 full size Cherokees, Wagoneers, and some J-series pickups and a few '84 up Grand Wagoneers till 1988.
Dana 300: The Dana 300 was used only in CJs from 1980 until 1986.
BW 13-39: The BW 13-39 "Quadra-Trac" was used in the CJ-7 from 1976 until 1979 and earlier in other models. It was introduced in 1973 in full size Jeep trucks (Wagoneers, Jtrucks and '74 to '79 Cherokee), but it was not used after 1979 in any Jeep trucks and only used behind the TH400 trans. The Quadratrac name was temporarily passed on to the '80-'82 NP219. It's demise came about due to Jeep switching to Mopar designed transmissions instead of the TH400 in an effort to gain fuel economy. AMC was already using the transmissions in their cars since 1972.
Dana 20: The Dana 20 was used in CJs from 1972 until 1979. It was introduced in larger Jeep trucks in the 60s, but it wasn't used in any Jeep trucks after 1979. It was only used with standard transmissions after '73. In 1980 it was replaced with the NP208J.
Dana 18: The Spicer/Dana 18 was used on the first CJs and their military counter parts until 1971. It was also used on all other trucks until around 1965.
NP-229 NP-228: The NP229 was used in '84-'87 except the end of '85 to mid '86 (replaced with the NP228 which was the same case, but no viscous coupler) with the AMC 4 cyl and was designated as the "Selec-Trac" transfer case in XJ Cherokees and XJ Wagoneers. It was also used mid '82 to '91 in full size Jeeps as the "Selec-trac" option. It uses a vacuum accuated 2wd/4wd flip switch on the center console (or dash) routed directly to the transfer case, while the lever reads H-N-L. Early models had a lockout to keep from shifting while moving because the vacuum front axles had to be engaged or extreme viscous couple damage would occur (in some cases within a minute!)
NP219: The NP219 (aka in FSJ circles as the "fake" Quadratrac because it wasn't Borg Warner made) was used as an option '80 to early '82 in Full Size Jeeps.
NV-249: The NV249 was used as a "Quadratrac" option in '93 up Grand Cherokees.
NP-241OR: Used in Jeep Rubicon '03 to date, this Command-trac type (officially known as Rock Trac) case features 4:1 low range and heavy duty internals (the tcase was originally designed for Cummins diesel)