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Transfer Case Doubler Kit - Double Down

Posted in How To: Transmission Drivetrain on May 1, 2007 Comment (0)
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Here you can see our completed 203/205 doubler setup. Though not quite as compact as some other low-gear transfer-case arrangements, this unit with its massive helical gears and large input/output shafts can survive under serious abuse and high horsepower.

Designed for fullsize trucks or other heavy-duty/high-output applications, the ORD doubler transfer-case system consists of three stout parts: the gearbox section from an NP203, the ORD adapter plate, and an NP205 transfer case. This system provides an additional low-range ratio of 2:1, which, when added to the existing NP205 low-range ratio of 2:1, equates to a final crawl ratio of 4:1. This combination of gearing gives any applicable vehicle improved crawl control and torque multiplication without affecting your high-range cruising speed and rpm. Thanks to the popular use of the NP205 transfer case in Chevy, Ford, and Dodge pickups, this setup can work in a bunch of different applications. The system uses a combination of trail-proven, readily available factory parts, along with a few custom components built by ORD. We like the fact that the system was designed to handle big-block power without grenading. But most of all, we like the fact that this complete 4:1 system costs significantly less than other low-gearing transfer-case options available today. Altogether, this project would have cost us $1,629 to complete (not including labor).

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4. With the NP205 we had it was necessary to do some minor machine work on the input-bearing retainer (case). This was due to the fact that our 205 originally came behind an SM465 transmission. ORD supplied us with the necessary parts to convert our 205 to the beefier Turbo 400 version. The machine work ensured fitment of the new larger Turbo 400-style input bearing and shaft. To do this, we had to completely disassemble the transfer case. Once apart, we had the empty case magnafluxed in preparation for machining. Here, you can see the material being taken off by an end mill.

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The doubler transfer case is not an afternoon bolt-in because of all the little details involved. Some things that should be addressed are:

Floorboard clearance
You may need to modify your floorpan, install a short body lift, or lower the transfer case to get the proper floorboard clearance with this kit in some vehicles. A combination of the above may work also. Floorboard clearance is rarely a major problem, but you should be aware of the possibility. We found the ORD Triple Stick shifter worked out nicely between the two front seats of our buggy donor vehicle. However, this may add a significant amount of time to the installation process in other vehicles.

Crossmembers
Crossmember modification will likely be required due to various frame changes when the crossmember is moved. Also, while a single crossmember under the 205 is adequate, dual additional crossmembers are strongly recommended. The front crossmember will likely require a loop or tunnel for front driveshaft clearance. Custom fabrication is required to completely skidplate the transfer-case setup. Ideas on high-clearance crossmember mounting can be found on ORD's Web site.

Speedometer Cable
You may need a new speedometer cable to reach the transfer case in the new position. They are available from the dealership or a parts store.

Exhaust
Some exhaust systems run near the transfer case or driveshafts and will need to be modified for clearance.

Driveshafts
You will probably need a longer front and shorter rear driveshaft with the doubler setup. If your shafts are in good condition, you can probably just have them rebuilt to minimize extra cost. This is a good time to look at U-joint and yoke upgrades also.

Doubler kit $785
Rebuild kit for our NP205 $169
Used NP203 ${{{300}}}
ORD Triple Stick shifter $265
Machine work $60
Miscellaneous $50
Total $1,629

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