Toyota trucks and 4Runners are found much more frequently on trails these days than they used to be. A big reason for this surge in popularity has been the common availability of lower-ratio transfer-case gearing for these rigs. Dual transfer-case setups and low gearsets have been readily available for all gear-driven transfer cases.
But beginning with the '85 model, a chain-driven transfer case of lighter design was also used in automatic-transmissioned vehicles, and, from 1988 on, in V-6-equipped Toyotas (trucks with four-cylinder engines have come with either style, depending on type of transmission). Although several manufacturers have looked into the possibility of stuffing a lower gearset into one of these cases, doing so simply has not been practical.
Marlin Crawler has dual transfer-case setups for the older-style gear-driven transfer-case Toyotas. The Toyota transfer case has two major sections: the front reduction box, which selects between high and low gear ranges; and the rear portion, which selects between two- and four-wheel drive. In a dual-case setup, a machined-aluminum adapter plate mates a second gear-reduction box from a donor T-case to the front of the stock transfer case. Marlin Crawler also has a kit to add an older-style gear-driven transfer case to a newer-model truck that originally came equipped with a chain-driven transfer case.
However, until recently, if you had a Toyota Tacoma or newer-model 4Runner, you had no options for lower transfer-case gearing. Two factors lead to this situation. First, as noted, all Tacomas and newer 4Runners use a chain-driven transfer case. Second, when Toyota introduced the Tacoma in late 1995, its engineers moved the front output of the transfer case from the passenger side (where it had been since 1979) to the driver side. Marlin Crawler has come up with a solution for Tacoma owners that allows the installation of a dual-case setup that adds an additional 2.28:1 or 4.7:1 gear reduction for low-low transfer-case ratios of 5.9:1 or 12.1:1. The company's MC09 kit mates an early-style reduction unit to the back of your Tacoma's transmission and then mates the back end of the reduction unit to the front of your stock Tacoma's transfer case.
This allows you to keep the driver-side front driveshaft and still mate to your stock front axle assembly. Both outputs, however, are relocated about 8 inches rearward, necessitating lengthening the front driveshaft and shortening the rear driveshaft.The kit is available for both four-cylinder and V-6 applications, and for five-speed and automatic transmissions. With the addition of this new crawler kit, Tacoma and late-model 4Runner owners can now enjoy the benefit of low-low gears that other Toyota owners have had for a number of years. Owners can achieve final drive gear ratios of more than to 200:1.
Follow along as Rocky Gleason from Marlin Crawler shows us how one of the new Tacoma transfer-case kits goes together.
Here is the first of the custom adapters in the new Marlin kit. It comes with a double-roller severe-service bearing. This adapter allows the attachment of the early-model reduction box to the front of the Tacoma transfer case. | 
The 31-needle roller-cage bearing is installed on the new output shaft. Next, the low-range gear is added to the output shaft with the small teeth on the gear next to the matching teeth on the shaft. The thrust washer and single ball bearing are added to the shaft. Some grease is used when adding all pieces to provide some initial lubrication and to make assembly easier. The newly assembled output shaft is pressed into the reduction-box adapter. The ball bearing that supports the shaft comes preinstalled in the adapter. | 
With the output shaft installed in the adapter, the supplied snap ring must be installed down into the groove on the output shaft. The output shaft should have 0.004 to 0.010 inch of endplay. After flipping the adapter over, another roller bearing is installed into the geared end of the output shaft. The clutch sleeve is installed onto the geared end of the output shaft. Along with the clutch sleeve, a modified shift-fork assembly is installed into the adapter. |
Next comes the addition of the counter-gear assembly. It is tapped lightly to seat it into the bearing that is preinstalled in the adapter. The input gear is installed onto the end of the output shaft and seats into the small roller bearing in the shaft. This photo shows the complete reduction-box gear assembly on the front of the adapter. | 
With the gear assembly complete, the reduction-box housing is prepared. Five studs are installed in the housing. Next, the housing is placed over the gear assembly on the adapter and the studs pushed through the adapter. With the reduction box and adapter secured together with the supplied nuts and washers, here is what the front of the reduction box looks like. | 
The second adapter supplied in the kit is mated to the front of the reduction box. |
The reduction box is topped off with one of Marlin Crawler's new billet aluminum shifter bases. | 
Here is the completed dual-case assembly, ready for mating to the stock Tacoma transfer case. | 
Once mated to the stock transfer case, the dual-case assembly is secured using supplied nuts and washers. Here is a fully assembled dual transfer case. |
Here is the installed crawler setup and transfer case. The stock transmission crossmember is usually sufficient. The owner of this truck added an additional crossmember that bolts to the bottom of the new reduction box. | | |