If you’re building a fullsize truck for extreme off-road use like rockcrawling, then you’ve probably heard of the Doubler. A 203/205 Doubler involves mounting a NP203 reduction box in front of an NP205 transfer case for a compound low range and better off-road torque management. Offroad Design (ORD) has long been the go-to place for rebuilt 203 boxes, 205 transfer cases, and the appropriate adapters to install them in fullsize 4x4s. But what if there could be something better? To make a stronger gear reduction box, ORD went back to the drawing board and developed the new Magnum Box. This planetary reduction box is smaller, lighter, and yet equal in strength if not stronger than the old Doubler. It has more options for gearing, adaptation, and wheelbase fitment. The Magnum Box is a step above and beyond the Doubler and fixes the minor weak links that the Doubler has. ORD has even gone so far as to recommend this box for more than just fullsize GM, Ford, and Dodge trucks. If you’re building a big-power, heavyweight Jeep Wrangler, for example, this may be just what you need for optimal gear reduction. We stopped by ORD to see a prototype unit assembled and got exclusive first shots of the guts of the Magnum. The Magnum Box is a six-pinion planetary gearbox designed to go in front of a 205 transfer case. The Magnum has a 2.72 low range and a tough 61⁄4-inch-long aluminum case.The Magnum Box is a six-pinion planetary gearbox designed to go in front of a 205 transfer The input shaft (top right) that runs between a 203 reduction box to a 205 transfer case input gear (top left) in a Doubler is very stout, but there is a point where it necks down to 1.29 inches at the 32-spline input. This can be a weak link when running the 203 in low range and the 205 in high gear. The Magnum intermediate shaft (middle and bottom) is massive at 1.63 inches, big enough to be run in any gear without fear of breaking it.The input shaft (top right) that runs between a 203 reduction box to a 205 transfer case i The 203/205 Doubler, seen here behind a TH350 automatic, is the old standby for low gearing in fullsize trail trucks with a 1:1 high range, a 1.96 mid range, and a 3.94 low range. But although it is strong it has a few disadvantages. First is the weight; the 203 gearbox alone is 93 pounds. The length of the TH350, 203, and 205 is 44 inches (221⁄4 inches for the 203/205 alone).The 203/205 Doubler, seen here behind a TH350 automatic, is the old standby for low gearin The Magnum is more expensive than a 203/205 Doubler, but it has some clear advantages—not the least of which is that it’s built from all new parts, unlike a used or rebuilt NP203. The gearing options are a 1:1 high range, 1.96 mid range, 2.72 low range, and 5.33 compound low range. The Magnum box weighs just 34 pounds, but the larger intermediate shaft makes it as strong as or stronger than a 203/205 setup. The shorter Magnum case also reduces the TH350/Magnum/205 assembly to just 42 inches (201⁄4 inches for Magnum/205 alone).The Magnum is more expensive than a 203/205 Doubler, but it has some clear advantages—not The 203/205 Doubler has long been the go-to set up for GM, Dodge, and Ford trail rigs. Offroad Design’s Magnum opens up a new range of options for transmission adaption with 21-, 23-, 24-, 27-, 29-, 31-, 32-, and 34-spline input available. With a long enough wheelbase (we’d recommend 103-plus inches minimum) you could swap this into a just about any 4x4 and have one of—if not the—strongest multiple gear ratio transfer case systems on the market.The 203/205 Doubler has long been the go-to set up for GM, Dodge, and Ford trail rigs. Off SOURCES Off Road Design 970-945-7777 offroaddesign.com/ By Fred Williams Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
