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Toyota Transfer Case Upgrade - Building A Better 'Yota 'Case

Case Housing
Harry Wagner | Writer
Posted October 31, 2006

More Than Just Gearing

Geardriven Toyota R1FA transfer cases benefit from huge aftermarket support. These transfer cases were used in four-cylinder pickups and 4Runners from 1979 through 1995. Thanks to the aluminum cast construction, these cases are lightweight (70 pounds), and with all gear internals, they are plenty strong. Even with motor swaps and 1-ton axles becoming more common under Toyotas, rarely does anyone feel the need to swap out the stock transfer case.

Now that you've decided to keep your Toyota transfer case though, how do you decide what products you need in order to conquer the toughest terrain? Worry not, Off-Road has rounded up information on some of the many aftermarket components available for the R1FA transfer case.

The R1FA transfer case is a split unit, with the front half providing gear reduction and the rear half controlling the engagement of four-wheel drive. Dual transfer case adapters mate the gear reduction half of the case to a complete transfer case, allowing twice the gear reduction when both cases are in Low range. With all of these adapters, expect to cut a hole in the floorboard for the additional shifter and make modifications to the driveshafts and speedometer cable.

Advance Adapters makes cast-aluminum transfer case adapters that are available from a variety of vendors. These adapters have been in production longer than any of the competition's and are also the most widely used at this time. The adapters are available for both 21- and 23-spline transfer cases and use bearings that are standard across the Advance Adapter product line for easy replacement, should that become necessary.

Inchworm machines an adapter plate from solid billet 6061-T6 aluminum, while the coupler shaft is machined from a factory output shaft. The Inchworm adapter is machined to close tolerances - parts fit right, run true, and last a long time. Together, the adapter plate and extra Toyota reduction box are about 6-3/8 inches long. This adapter uses factory Toyota bearings for easy replacement if necessary.

Marlin Crawler offers a cast-aluminum dual transfer case adapter featuring double roller bearings and an oversized billet mainshaft. The double roller bearing is 5/8 inch wider than the competition's and has two sets of rollers, amounting to 32 total bearings, compared to the standard nine. Marlin also preassembles its adapter plate by pressing in the double roller bearing, installing the three bolts on the mainshaft, pressing in the supplied cage roller bearing and lubing it, and installing the necessary dowel pins. The company even supplies a shift light plug with gasket and a new genuine Toyota transmission output seal.


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All-Pro Off-Road
Hemet, CA 92543
Inchworm Rock Walkin' Gear
Shingle Springs, CA 95682
Marlin Crawler
Fresno, CA 93703
Advance Adapters Inc.
BudBuilt Frames & Accessories
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