We all know that the NP205 is the king of brute transfer cases. Huge gears and a cast-iron case give it legendary strength. The NP205 was used by almost every fullsize truck manufacturer at one time or another and is frequently swapped into vehicles that chew up and spit out lesser transfer cases. Yet modifications and cool aftermarket parts for the 205 are limited to say the least; nonexistent is more like it. Why are there no low-range gears for it, or even a twin-stick shifter?
We got tired of waiting so we built our own twin-stick, in addition to modifying the shift rails for front-wheel-drive high and low, and rear-wheel-drive low. These added functions will decrease the turning circle of your vehicle in tight-quarters wheeling. Shifting to front-drive-only with the emergency brake locked will allow the vehicle to practically pivot in a circle. Those with Dana 44s and lockers will need to go easy on the throttle to keep steering joints and axleshafts from shattering. Dana 60 owners should be able to let it all hang out. Up until now the Atlas II was the only transfer case widely available with this capability. An Atlas transfer case isn't cheap and it is not recommended for fullsize trucks for strength reasons.
You can convert your NP205 to a twin-stick without completely disassembling the transfer case. We modified a Currie twin-stick shifter for a Dana 300 to fit our divorced NP205. This shifter assembly can be modified to fit married 205s with a little ingenuity, or you can build your own.
We have seen a few NP205s that have been modified to perform the same functions by removing the interlock pills. Without the pills in place the transfer case can be shifted into front-wheel low and rear-wheel high or vice versa. Needless to say, this is bad. Spinning the front and rear driveshafts at different rates will cause something to break. By modifying the range shift rail as shown, the interlocks will prevent you from being able to shift the transfer case into these breakage-prone positions. The new shift pattern for NP205s with passenger-side front outputs (Dodge and GM) is shown above. Ford 205s will have the rear-wheel shifter on the right but all other functions are the same.
1.) It's easiest to perform...
1.) It's easiest to perform the modification with the transfer case removed from the vehicle. The P.T.O. cover plate is removed for access to the inside of the transfer case.
2.) Remove the detent ball...
2.) Remove the detent ball and spring from the range shifter. The range shift rail is the one closest to the input and rear output of the transfer case. A magnet is useful in removing the ball and other small parts encountered during the process.
3.) A 1⁄4-inch freeze-plug...
3.) A 1⁄4-inch freeze-plug seals the access hole to the roll pin that holds the range shift fork to the shift rail. Tap the plug and the roll pin out of their seats and into the case. They can be collected through the P.T.O. opening.
4.) Install an Allen wrench...
4.) Install an Allen wrench or wire to hold the shift fork in place, and remove the range shift rail.
5.) The interlock detents...
5.) The interlock detents in the range shift rail need to be modified. The marked areas are where the rail needs to be ground.
6.) This is the completed...
6.) This is the completed job. The detent on the tip should have an abrupt slope and the other detent should have a gradual one as shown. The rail can then be installed opposite of removal.
7.) We cut the finger off...
7.) We cut the finger off of our range shifter to simplify our linkage installation. The original single lever shifter will no longer work.
8.) This twin-stick kit...
8.) This twin-stick kit and optional shift boot from Currie is designed for a Dana 300. With a little backyard ingenuity it can work on divorced and married NP205s.
9.) The Currie linkage bolts...
9.) The Currie linkage bolts onto the 205. We mounted our Currie shifters to the transmission crossmember and had to extend this linkage about a foot.