TEXT AND PHOTOS BY JERRY SLATTERY  (Photos from story)
from StreetTrucks Magazine (March, 2001)

Just using the word truck usually indicates the vehicle can have more then one purpose. One of the other purposes is usually towing. With towing weights as high as 10-15,000 pounds it's pretty hard, with the horsepower available today, to have enough gearing for low speed pulling and still be able to cruise economically at freeway speeds. If you are a multi-purpose truck owner, and most of us are, you’ll be interested to know that you now have some gearing options.

The strongest gear driven overdrive or underdrive two-speed auxiliary transmission on the market, the Dual Range, offers a pulling capacity of over 35,000 pounds gross combined vehicle weight. You can double the number of forward and reverse gears with this shift on the fly unit. Whether you have a class A RV, 4WD, dually pickup, 3/4-ton or larger towing pickup, or a cool street truck for occasional hauling, and would like to have a 20-percent under or over “gear-splitter”, your dream just came true.

The manufacturer of the Dual Range (20-percent overdrive or 20-percent underdrive) auxiliary transmission, United States Gear Corporation, has been a transmission and transmission component manufacturer since 1963. This family owned and managed business has grown to fill a 450,000-square foot manufacturing facility consisting of three divisions and employing more then 400 people! For about 20 years, U.S. Gear was primarily a service company manufacturing components for GM, Ford, Chrysler, Caterpillar, Allis Chalmers, Eaton, Rockwell, and Clark Equipment. From the experience gained working with these elite customers, U.S. Gear saw the missing link in the towing market: not enough gears for the amount of horsepower or not enough horsepower for the amount of gears. Their solution: split all the gears, which would double the amount of existing gears.

The Dual Range was originally developed by Doug Nash in early-80s. By the late-80s, U.S. Gear began manufacturing the Dual Range for Milemarker, and by the early-90s U.S. Gear continued manufacturing and took over the marketing of the Dual Range under the U.S. Gear name. They realized by manufacturing one basic gear box, either under or overdriven, they could fit all diesel or gas powered American pickups, larger trucks up to 1 1/2-ton (GVW), and class A motor homes (18-19,000 GVW) inexpensively with adapters to mate to all of the different applications, including 4WD, three- and four speed-automatics with overdrive and four- and five-speed manual transmissions with an overdriven high gear. This would provide vehicles with the right gearing for every situation and allow the use of overdrive in the automatics.

Even though most vehicles come standard with overdrive automatics today, most car manufacturers will prohibit towing in the overdrive position. By adding the low speed (underdriven) version of the Dual Range, the factory transmission becomes a real pleasure to drive. Not only do you gain the pulling power needed for towing, but you can actually use that power in the factory automatic (30-percent) overdrive mode as well.

Shifting while driving or ‘shifting on the fly’ is a breeze! While the vehicle is moving and the driveline under a load, you simply push the gearshift-mounted button for automatics or pull the button mounted on the floor shift arm of the standard transmission and wait two seconds while the Dual Range loads the next gear. With the automatic transmission, you simply lift your foot quickly to about half-throttle and then back down again, you’ll feel the next gear engage. On standard transmissions, after you push the button (waiting a couple of seconds), all that is needed is a quick, slight depression of the clutch to allow the Dual Range to shift into the next desired gear. The quick shifts with this unit will keep your horsepower and torque loss to an absolute minimum. Check the photos for mounting the electronics.

Since the Dual Range is just under 12 inches long, it will be necessary to shorten the driveshaft. It is very important to record your original driveshaft angles before disassembly. The goal here is to try to duplicate the original angles to retain original specifications and smoothness. On short 4WD vehicles, the finished driveshaft length should not be less than 12 inches.

Depending on which unit is installed in your vehicle (under or overdriven), it may be necessary to change the speedometer gear. To read accurately, since the speedometer cable is now connected to the speedometer gear in the auxiliary transmission, a correction formula and procedure for mechanically geared speedometers is included with the kit.

The installation shown here is focused on the ‘94 and later Dodge 4WD short-bed with manual transmission, Cummins NV 4500 diesel pickup (kit #80-80085). As you’ll see in the photos, the installation is typical except for the length of the Dodge gas tank. The long fuel tank which runs parallel with (and inside) the framerails needed to be shortened, and a little trimming on the floor brace was also needed. A small center notch must be removed to make room when the transfer case is moved back by the additions of the Dual Range between the truck’s transmission and the transfer case.

Installing the unit is most easily accomplished on a drive-on style rack or a drive-over pit. If you have ever changed a clutch on a standard transmission vehicle and understand automotive chassis basics, you are more than qualified to do this job in your garage at home with the use of a floor jack and jack stands. You could perform the installation with less experience, since complete instructions and a direct line to U.S. Gear’s tech department are provided. Or you can call for the nearest installation dealer in your area.