By building a strong aluminum adapter plate, Marlin Crawler is able to bolt an additional reduction housing unit between your existing transfercase and transmission with each case having its own shifter. By combining the factory Toyota transfercase low range reduction gear sets of 2.28:1, a final transfercase ratio of 5.2:1 is achieved. This new low range gear ratio is 119% lower than a stock setup.
Each of the two reduction housings can accept either the stock, 4.00:1, or our Marlin Crawler 4.70:1 gear set. With the dual case setup you will also have access to 2WD low range, which is very useful on the trail between major obstacles, or while towing boats out from steep lake docks. Having dual cases gives you access to 20 forward gears and 4 different reverse gears (with a 5-speed transmission).
The second case and adapter plate measures to only 6 «" long. Except for reworking the drive shafts, it's a fairly easy installation. The adapter flanges are 5/8" thick. The cross member is able to remain in its original factory mounting location. Depending on the application, the second shifter rests 6«" to 11" behind the transmission, and the third shifter will rest 6«" to 10" behind the crawl box. Other locations for the second shifters are available by using Off-Set shifter kits and Short Throw shifter kits.
In our opinion, the Ultimate setup is when a dual transfercase is built with one set of stock gears (2.28:1), and one set of Marlin Crawler's 4.70:1 gear sets. This is known as the Dual Ultimate Crawler. In a 21-spline application, due to the excess torque generated by the 4.70:1 gears, we will only build a 21-spline Ultimate Crawler with the 4.70:1 gears in the back case. But in a 23-spline application, the factory 23-spline input is much stronger, and therefore, the 4.70:1 gears can be placed in either the front case or in the rear, the choice is yours. In any of the available applications, two sets of 4.70:1 can be used to achieve a low range crawl ratio of nearly 500:1! More than 9 times lower than stock! We call this a Dual Ultimate Overkill Crawler since such a low crawl ratio is merely for bragging rights.
With a dual transfercase setup, the front shifter is simply a high/low shifter. High range is 1:1, and Low range is 2.28:1 (or 4.00:1 or 4.70:1). The rear shifter is the same "J" pattern you have now, with High range as 1:1, and Low range as 2.28:1 (or 4.00:1, or 4.70:1).
With the addition of just the Marlin Crawler Dual Transfercase Crawler to your vehicle, you have the ability to leave one shifter in Low Range, and the other in High Range. And as you might have guessed, this would be the same ratio that you are now. So you would still be able to keep up with your friends when you come to these long flat dirt stretches between obstacles. And then, with the push of the second lever into Low Range, a new transfercase overall ratio of 5.20:1 enables your vehicle to crawl at gear ratios only dreamt of.
With a Marlin Ultimate Crawler setup you can place one case in low range (2.28:1) and use stock 4WD low range. You can also use just the 4.70:1 gears and keep the other case in High range, giving you just over twice the low range gearing of stock. For the really tough trails, or whenever the trail demands more torque, traction, timing, or control, you can put both cases in low range and have 4.5 times the reduction of the stock case.
The ability to shift each lever separately gives you the following low range options:
Stock 4 Cyl
Stock 6 Cyl
Single case with 4.70 gears
Dual case / stock gears (2.28 & 2.28)
Dual case / stock (2.28) and 4.70 gears
Dual case / two sets of 4.70 gears
Triple cases can also be done
Overall T/case ratio (low range)|
2.28 and 5.20
2.28 and 4.70 and 10.70
4.70 and 22.09
2.28, 4.70, 5.20, 10.70, 22.09, and 50.36
This chart helps you to see all the common crawl rations available from stock and modified dual crawlers. Start by finding the column with your ring and pinion ratio at the top. All ratios are based on a 3.93 first gear ratio, the most common Toyota 4WD first gear transmission ratio. Other common Toyota first gear ratios are 3.83, 3.95, 4.31, and 5.15
|2.28 X 2.28||80:1||84:1||89:1||93:1||100:1||108:1|
|2.28 X 4.70||164:1||173:1||184:1||192:1||206:1||223:1|
|4.70 X 4.70||338:1||356:1||379:1||396:1||424:1||459:1|