Jeep Quadra-Trac: How It Works
Q I bought a '73 Jeep Wagoneer with what is called a "Quadra-Trac" transfer case. All I know is that it is a full-time system. Luckily, the owner's manual was in the vehicle, so at least I understand how to use it. Are you familiar with it? Can you explain more to me about how it works?
San Diego, CA
A Sometimes, short questions like this take up a lot of space to answer, so here it is. It was made by Borg-Warner, and for its time was way ahead of anything else on the market. There were two models: A two-speed 'case with a 2.57:1 low-range gear which was referred to as the Model 1339, and a single-speed case, the Model 1305. It was used in full-size Jeeps such as your Wagoneer from 1973 to 1979, and in CJ-7s from 1976 to 1979. The two-piece aluminum case uses drive sprockets and a drive chain very similar to present day transfer cases. Within the case is what's referred to as an "unloading" cone-clutch limited-slip differential from which power to both front and rear is transferred.
Inside the limited slip, which is not unlike some present-day rear locking differentials, are some clutch plates preloaded by what are referred to as Belleville springs. When excessive torque loads are applied, such as going around a corner or differences in traction are encountered, they will slip, thus allowing a smooth transition of power. When one axle has less traction than the other, power will be applied to the axle with the most traction.
Under situations where you want to lock out this transfer of power, front to rear, it can be easily done by using the emergency lock switch. This switch, I believe, is found in the glove compartment and is vacuum-operated. These had a high failure rate, so I am sure yours does not work being that it is some 37 years old now. Jeep did make a conversion kit to allow manual shifting, but this kit is long out of stock. With a bit of ingenuity, I am sure one could make his own. It does nothing more than lock out the clutch action, providing a direct power path to each axle.
Like any part-time system, when "locked," it should not be operated on a dry or hard-surface road.
The big drawback of the Quadra-Trac is that when driven on straight roads for long distances without any reason for the clutch packs to release, the clutch packs would build up a varnish and had a tendency to stick. When you did turn, the clutchpacks would then release with enough intensity to cause a banging noise that the hollow driveshafts enhanced. This was commonly referred to as a "slip-stick" situation. Sometimes it's necessary to find a big empty parking lot and do several figure-eights in both directions that will force the clutches to slip to relieve this problem.
For whatever reason, drivechains only last about 60,000 miles before they need replacement. This is most likely caused by the occasional shock-loading of the clutch pack when it has a hard release. You will definitely know when the chain needs replacing-it will actually jump on the drive gear.
Another problem, which also often leads to increasing the slip-stick problem, is the fact that this case takes a special fluid. No, most likely you can't order it from your local Jeep dealer; the parts department probably doesn't even have a clue about it. A company called Crown Automotive does manufacture the proper fluid, and it can be purchased through specially shops that deal with Jeep vehicles.
I believe that Novak Conversions (435/753-2513, www.novak-adapt.com) has the fluid, as well as rebuilding kits for the case. They also offer a kit to swap it over to a Spicer 18 transfer case. The Jeep 18 is the only transfer case to use here as both front and rear drive outputs are in line with each other. Some people have used the Jeep Dana 20 transfer case, but this puts the rear driveshaft at an angle that could lead to excessive vibration. Mile Marker (800/886-8647, www.milemarker.com) still makes special kit to eliminate the clutch pack.