Offroad Design Doubler Build
How low can you go?
Not many upgrades provide more trail prowess than low gearing, and few gearing options can match the strength of an Offroad Design Doubler. The Doubler uses an NP205 transfer case, which is a gear-driven transfer case with an iron housing and adds the gear reduction half of an NP203 transfer case in front of it. This effectively doubles your low range, with the NP203 offering a 2:1 reduction and the NP205 providing 1.96:1 low range. Combined, they make 3.92:1 double low for increased torque multiplication and control.
ORD’s Doubler has become common on fullsize Chevys used for hardcore trail use, and we wanted to put one into Raymond, the F-150 I entered in our Cheap Truck Challenge (“Raymond,” Oct. ’13), as part of the truck’s extreme makeover at Nate’s Precision. When we talked to ORD owner Stephen Watson about our plan, he asked if we already had the Ford NP203. “Well, not yet,” we replied. “Call me back when you have one in your hands,” he told us.
It turns out he was right. The most difficult part of putting the NP203 transfer case between our NP435 transmission and factory NP205 was finding a Ford NP203 transfer case with the appropriate 31-spline input gear. Chevy applications are typically 10-spline (SM465), 27-spline (TH350 and 700R4/4L60), or 32-spline (TH400 and NV4500) and are fairly common, with even new components available. That is not the case for the Ford NP203 transfer cases', which were only offered from ’74 to ’79, and even then they were far less common than the NP205.
Bayshore Truck eventually found us a Ford NP203 transfer case—but it was halfway across the country. Rather than eat the shipping on a 200-pound transfer case, we just purchased the Ford-specific input gear and installed it in a locally sourced (and more common) Chevy NP203 transfer case . Once we rounded up the appropriate input gear, the Doubler came together quickly with help from Offroad Design, Bayshore Truck, and Nate’s Precision.