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Offroad Design Doubler Build

Posted in How To: Transmission Drivetrain on April 18, 2014 Comment (0)
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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.

1. Although the transfer case can be removed while the truck is on the ground, the crew at Nate’s Precision did it the easy way with a tranny jack and a lift. They also removed our NP435 transmission so we could rebuild it at the same time. 1. Although the transfer case can be removed while the truck is on the ground, the crew at Nate’s Precision did it the easy way with a tranny jack and a lift. They also removed our NP435 transmission so we could rebuild it at the same time.
2. Only the gear-driven range box of the NP203 is used for the Offroad Design Doubler, not the huge chain-driven 4WD portion of the box. These cases are still relatively inexpensive and easy to find for Chevy applications. 2. Only the gear-driven range box of the NP203 is used for the Offroad Design Doubler, not the huge chain-driven 4WD portion of the box. These cases are still relatively inexpensive and easy to find for Chevy applications.
3. NP203s out of Fords are rarer than hen’s teeth, so we had to do a lot of searching before we came up with this 31-spline Ford input gear. We are running an NP435 manual transmission, but C6 automatics have the same spline count. 3. NP203s out of Fords are rarer than hen’s teeth, so we had to do a lot of searching before we came up with this 31-spline Ford input gear. We are running an NP435 manual transmission, but C6 automatics have the same spline count.
4. It was cheaper to ship the Ford input gear rather than the whole transfer case, so Dan Aguilar at Bayshore stabbed the gear into a Chevy housing. He called in a favor from machinist “Uncle Gerry” to redrill the mounting pattern on the front of the Chevy case to match our Ford transmission, but you could do it with a drill and a tap as well. 4. It was cheaper to ship the Ford input gear rather than the whole transfer case, so Dan Aguilar at Bayshore stabbed the gear into a Chevy housing. He called in a favor from machinist “Uncle Gerry” to redrill the mounting pattern on the front of the Chevy case to match our Ford transmission, but you could do it with a drill and a tap as well.
5. The Offroad Design adapter is a work of art. The single piece of billet 6061-T6 aluminum is machined in house at ORD’s facility in Colorado to ensure the utmost quality. Also note the thorough installation instructions that make the entire process easy to follow. 5. The Offroad Design adapter is a work of art. The single piece of billet 6061-T6 aluminum is machined in house at ORD’s facility in Colorado to ensure the utmost quality. Also note the thorough installation instructions that make the entire process easy to follow.
6. This billet chromoly steel shaft is included to connect the NP203 to the 205. It is all new, not a resplined factory shaft that some companies offer. 6. This billet chromoly steel shaft is included to connect the NP203 to the 205. It is all new, not a resplined factory shaft that some companies offer.
7. Dan Aguilar at Bayshore also disassembled our NP205 to install the new ORD shift rails for our twin stick shifters. Like the intermediate shaft, the shift rails are new components, not modified stock parts. 7. Dan Aguilar at Bayshore also disassembled our NP205 to install the new ORD shift rails for our twin stick shifters. Like the intermediate shaft, the shift rails are new components, not modified stock parts.
8. By decoupling the shift rails in the NP205, we have the ability to run in 2WD Low, or engage just the front axle as well. This is a huge benefit for maneuvering a fullsize truck around tight trails. 8. By decoupling the shift rails in the NP205, we have the ability to run in 2WD Low, or engage just the front axle as well. This is a huge benefit for maneuvering a fullsize truck around tight trails.
9. Bayshore prides itself on the details for every job, whether it is regearing a Jeep or building a transmission for an over-the-road truck. Bayshore even made these personalized ID plates for our ORD Doubler. 9. Bayshore prides itself on the details for every job, whether it is regearing a Jeep or building a transmission for an over-the-road truck. Bayshore even made these personalized ID plates for our ORD Doubler.
10. Once the Doubler was assembled we headed back to Nate’s Precision to stab it in the Ford. Nate Jensen and crew used a durable polyurethane tranny mount from Energy Suspension as the foundation for a custom crossmember. 10. Once the Doubler was assembled we headed back to Nate’s Precision to stab it in the Ford. Nate Jensen and crew used a durable polyurethane tranny mount from Energy Suspension as the foundation for a custom crossmember.
11. Offroad Design built our adapter with a 2-inch rotation to make the bottom of the NP205 flush with the NP203. This gave us increased ground clearance that Bernie Dettrich at Nate’s Precision maximized on when building the custom tubular crossmember for the Doubler. A skidplate was added to the framework after this photo was taken. 11. Offroad Design built our adapter with a 2-inch rotation to make the bottom of the NP205 flush with the NP203. This gave us increased ground clearance that Bernie Dettrich at Nate’s Precision maximized on when building the custom tubular crossmember for the Doubler. A skidplate was added to the framework after this photo was taken.
12. The twin sticks for the NP205 use rod ends for precise shifting and come up through the factory location in the floor. The shifter for the NP203 can be mounted remotely anywhere on the floor using the supplied ORD hardware. 12. The twin sticks for the NP205 use rod ends for precise shifting and come up through the factory location in the floor. The shifter for the NP203 can be mounted remotely anywhere on the floor using the supplied ORD hardware.
13. The final step was to measure for new drivelines and head back to Bayshore Truck. They built us heavy-wall drivelines with 1350 CVs at the transfer case and flanges to mate up to the NP205. 13. The final step was to measure for new drivelines and head back to Bayshore Truck. They built us heavy-wall drivelines with 1350 CVs at the transfer case and flanges to mate up to the NP205.

Sources

Energy Suspension
San Clemente, 92673
888-913-6374
http://www.energysuspension.com
Offroad Design
970-945-7777
www.offroaddesign.com
Bayshore Truck Equipment Co.
775-331-6605
http://www.bayshoretruck.com
Nate’s Precision
755-358-2555
plus.google.com

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