For 1973, the full-size Jeep Wagoneer gained Jeep Quadra-Trac, a full-time four-wheel-drive system. Before that, a Wagoneer driver had to shift a transfer case and lock the front hubs by hand. With Quadra-Trac, all four wheels drove all the time. Meanwhile, the system split torque between the axles on its own.

The system also arrived at a turning point for the brand, a few years after American Motors bought Jeep. Here is how the hardware worked and how long it lasted.

One claim stays out of this story. None of the sources read for it call Quadra-Trac the first full-time four-wheel-drive system, so this article doesn’t either.

The Wagoneer before Jeep Quadra-Trac

The Wagoneer was already a decade old when Quadra-Trac arrived. Wikipedia’s Wagoneer (SJ) history says it launched in November 1962 for the 1963 model year. Soon after, in early 1963, Willys Motors renamed itself Kaiser Jeep Corporation.

Then, in early 1970, AMC acquired Kaiser Jeep and began upgrading the range, the same entry says. Quadra-Trac followed in 1973. According to Wikipedia, it removed the need for a manual-shift transfer case and manual locking hubs. In turn, it broadened the appeal of Jeep products.

How the Borg-Warner case split the power

Quadra-Trac’s hardware came from Borg-Warner. Wikipedia’s guide to Jeep four-wheel-drive systems describes it as a chain-drive system introduced in 1973 on the full-size Jeep line. It used two transfer cases, the BW1305 and the BW1339, and paired them with AMC’s version of the Turbo-Hydramatic 400 automatic.

A full-time system needs a way to let the front and rear axles turn at different speeds. The International Full Size Jeep Association’s transfer-case guide explains that full-time mode uses a differential between the front and rear driveshafts. As a result, the truck could run on high-traction, low-traction and mixed surfaces.

Keeping both axles pulling

A plain differential was only half the answer, though. For that reason, IFSJA says, full-size Jeep full-time cases used a device to limit slip between the driveshafts. That way, at least two wheels kept some power.

Wikipedia names that device in the BW1305 as a cone-type slip-limiting clutch, which distributed torque between the front and rear outputs. That center limited-slip set Jeep’s unit apart from the open New Process NP203 used by Dodge, GM and Ford, the entry adds.

For deeper mud or snow, the driver could also lock the center differential. JeepFan’s Quadra-Trac explainer calls it a vacuum-operated lock. In a CJ, it notes, the switch sat in the glove box.

Low range: the BW1305 vs the BW1339

Not every Quadra-Trac Jeep had a low range. The BW1305 offered only four-wheel-drive high, in full-time or locked modes, JeepFan says. By contrast, the BW1339 added a 2.57:1 low range through a planetary reduction at the rear of the input shaft.

IFSJA confirms that low range was optional on the 1973–1979 Quadra-Trac systems. With it, Wikipedia lists five modes: 4WD High locked, 4WD High open, Neutral, 4WD Low open and 4WD Low locked.

Later changes to the Borg-Warner cases

The two cases were closely related. In fact, JeepFan says a BW1305 could gain low range by adding the same planetary reduction the BW1339 used. Both cases also had offset yokes that exited on the passenger side, the site adds.

Some owners later went the other way. IFSJA lists a Milemarker part-time conversion for the BW1339, which added two-wheel-drive high and low modes. Unlike the factory setup, that conversion gave up full-time operation.

Which Jeeps used it, and what replaced it

The Borg-Warner Quadra-Trac went into the 1973–1979 Wagoneer, Cherokee and Gladiator, JeepFan and Wikipedia agree. In addition, the smaller CJ-7 offered it from 1976 through 1979.

For 1980, Jeep switched to a New Process NP219 case, still sold as Quadra-Trac. Wikipedia says it used a viscous center coupling and a 2.61:1 low range. It lasted on the full-size Cherokee, Wagoneer and Grand Wagoneer through 1982. Then, in 1983, Selec-Trac replaced it and added a two-wheel-drive mode.

Jeep never let the name go, however. JeepFan notes that Quadra-Trac returned on the 1993–1995 Grand Cherokee with an NP249 case. Later versions of the system followed on Jeep models after that.

Where the Wagoneer ended up

The full-size Wagoneer itself outlived the original Quadra-Trac by more than a decade. In 1984, Jeep renamed the Wagoneer Limited the Grand Wagoneer, Wikipedia says. Finally, the last one rolled out of the Toledo plant on June 21, 1991.

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This article was created with the help of AI and was reviewed and edited by Fast Lane Only editors before publication.