Driveline and Airtime
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We originally planned to have our pre-runnin two-wheel-drive 79 Ford F-150 totally converted to a whumpin four-wheel drive in three issues. We did it, sorta. If you havent been following along we began the conversion in Two-by-Four, Part I (July 2000) by cutting off the original front suspension, choosing an axle and transfer case, building a three-link front suspension, and designing a steering system. We continued in Two-by-Four, Part II (Aug. 2000) with the coilover shocks and their mounting. What we have here is the completion of the project and some tips about what we would like to change and the stuff well live with.
Our original transmission was fine and had less than 5,000 miles on it since a rebuild. We have no idea how automatics work and we dont want to know, so we decided that a divorced transfer case was the perfect way to keep from tearing into the tranny. We called Boyce Equipment and ordered a divorced Dodge NP205. This version of the NP205 has four 5/8-inch, coarse-thread holes tapped in the top of the housing that make building a mount easy. We used 1 ½-inch 0.120-wall tubing for the main structure and 1-inch DOM tubing with a 5/8-inch hole to firmly secure four 5/8-inch bolts to the transfer case. Wrangler spring bushings fit inside the 1 ½-inch tubing and insulate transfer case vibrations much like standard mounts, only ours are stronger and less prone to wear.
To support the transfer case, we boxed one crossmember for strength and added mounting ears to it. It was originally used to support one end of the second (now removed) fuel tank. The other mount bolts to the side of the framerail. You may need to fabricate crossmembers depending on your application and where you mount the transfer case. The biggest advantage to using a divorced transfer case on our Ford was the ability to clock it without a custom adapter. This gave us extra ground clearance under the already-low transfer case. However, the oil filler needed to be extended up with a short section of pipe to provide proper lubrication. The dotted line indicates the oil level with the transfer case mounted in the factory application.
Since our NP205 was originally from a 1-ton, it came with monster 1350-series yokes on the input and rear output, while the front output is a 1310 series. We called Tom Woods Custom Driveshafts and gave the company our measurements for all three driveshafts (dont forget about the nubby unit between the transmission and transfer case). We also found out that we could have our shafts painted almost any color at no extra charge. Just to test that out we went for a powder blue in hopes that it would match the anodizing on the shocks. It didnt. We did have to clearance the rear 1350 yoke and driveshaft with a grinder to keep all 14 inches of rear wheel travel bind-free.
After eyeballing an exploded diagram of an NP205 we decided that it was possible to safely convert our shifting mechanism to a twin-stick for Atlaslike shifting abilities with bombproof strength (Twin-Stick 205, Aug. 2000). We built a bracket that holds the individual shifters and it bolts to the rear of the transmission. All-thread rod and miniature rod ends from the local hardware store make up the rest of the linkage. The twin sticks pop up through the floor and are sealed with a boot almost like original parts.
Dealin With It
There is a vibration coming from the nubby driveshaft. We tried shimming the tranny and transfer case and its better, but we still feel the vibration at 50-60 mph. Well eventually change the transfer case mounts so the divorced driveshaft has correct angles.
The transfer case probably hangs down too low for rockcrawling but its fine for bashing around trails and general off-road mayhem.
What We Changed
The 250-pound over 350-pound coils we originally chose left the truck sitting too high. We swapped them for 150-pound over 250-pound coils.
To read "Project Two-By Four, Part 1: Building a Three-Link and Converting Two-Wheel Drive to Four-Wheel Drive,"click here.
For "Project Two-By Four, Part 2: Shocks and Hoops," click here .