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Jeep Wrangler YJ - The Ultimate Dana 300 - Tech

Posted in Features on August 1, 2002
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From 1980 to 1986, the Dana 300 transfer case could be found in nearly every Jeep CJ rolling off the assembly line. The cast-iron, gear-driven T-case was (and remains) extremely tough, and with a respectable 2.62:1 Low-range in stock form, it was pretty trail-worthy. Although Jeep bid farewell to the 300 in '87 when the Wrangler YJ joined the lineup, this transfer case continues to be one of the most popular for hard-core enthusiasts.

As fine a transfer case as the Dana 300 is, though, it does have a few weak points; three to be exact: gear reduction, the rear output shaft, and ground clearance. All of which can be corrected with some great aftermarket parts that are designed to make the Dana 300 the ideal T-case for hard-core 'wheeling.

As we said, a 2.64:1 reduction isn't bad for a stock case, but if you want to tackle serious terrain with greater ease and agility, the TeraLow 4:1 gearset is the only way to go. Do some quick math and you'll find that this gear swap provides a 50 percent increase in crawl ratio, which translates into the ability to idle up steep rock faces that require technical maneuvering. No more will you have to throttle up big boulders or ride the brake on the way down. The low-speed torque the 4:1 gears provide will make your performance on the rocks much smoother and better controlled, which will almost certainly extend the life span of other parts on your rig.

The TeraLow 4:1 kit comes with five new replacement gears, a new rear output shift rod, and new seals and gaskets. The only modification required is a bit of grinding on the opening at the bottom of the case to accommodate the new intermediate gear. Tera also offers a Dana 300 overhaul kit, which includes bearings, snap rings, a new intermediate shaft, and shims. We highly recommend it. After all, unless the case has been recently rebuilt, everything inside is at least 16 years old.

The only real weak point on the Dana 300 is the rear output shaft. On a perfectly stock vehicle, it's fine. But once you start adding healthier engines, bigger axles and tires, 4:1 gearsets, and articulating suspensions that can cause the driveshaft to bind a bit, the 26-spline, 1-1/8-inch od shaft just doesn't cut it.

Fortunately, Advance Adapters has designed a new output shaft and aluminum housing assembly that completely replace the original components. Offering some genuine strength, AA's new 32-spline output shaft has a diameter of 1-3/8 inches and only adds a 1/2-inch to the overall length of the transfer case, which means that driveshaft modifications should be unnecessary.

Ground clearance is always an issue for four-wheelers. And anything that interferes with ground clearance is to be avoided or removed. That brings us to the final problem with the Dana 300: In stock position, it hangs a full 5 inches lower than the rear output shaft, making it the single biggest hindrance to running any kind of a belly plate that would make the underside of your rig rock-proof.

Once again, Advance Adapters has stepped up with a solution: the Dana 300 rotating ring. This aluminum ring will allow you to rotate the transfer case counter-clockwise to four different positions to increase your overall ground clearance. How far you decide to go depends on how much modifying you want to do in terms of body clearance, driveshaft angles, exhaust routing, and shifter linkages. If each of these were modified correctly, though, it would be possible to use a skidplate that runs flat from rail to rail. And it only adds 3/4-inch to the overall length of the drivetrain. The kit includes the adapter ring, a longer T-case input shaft and bearing, a gasket, and bolts.

Sources

Advance Adapters
Paso Robles, CA 93446
800-350-2223
www.advanceadapters.com
Tera Mfg.
801-288-2585
www.teraflex.biz
T&J's 4 Wheel Drive Center
Orange, CA 92687

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