- Article/photo's courtesy of:
- Steven JarvisConverting your NP205 from a single shift lever to a twin shift lever (twin stick) allows complete control of the front and rear axles. You can have the front in HI range and the rear in neutral or HI, or the rear in LOW range and the front in LOW or neutral or any other combination of HI, LOW and neutral. Some people take advantage of this functionality by using just the front wheels to pull the vehicle around tight turns on the trail. I have found it most useful to me to be able to put the rear wheels in low range and the front in neutral when easing around on the trail, especially on dry trails where 4x4 is not needed.
JKW Offroad 205 Twin Stick Review
JKW OffRoad offers a heavy duty twin stick kit just for this application as well as a pair of brand new shift rails modified for full twin stick functionality. The twin stick is a simple design consisting of (4) basic parts, two shift levers and two rail brackets. The kit is designed to fit the 73-87 GM NP205 transfer case mounted behind the SM465, TH350 and TH400 transmissions. Parts are machined from SAE1018 steel and jig welded for accuracy. The shift rails are brand new (not welded and machined stock rails), made from turned, ground and polished heat treated alloy steel. The rails have the correct notches machined in to allow full twin stick functionality and still maintain the safety of not being able to put the axles in HI and LOW at the same time. The twin stick kit also comes with a new greaseable pivot bolt. The bolt is specially made for twin shifters by providing a dual grease path for each of the shift lever pivots.
The twin stick installation can be done with basic hand tools – no special tools required. Here’s a picture of the tools I used. The hardest part of the installation is removing and reinstalling your heavy NP205 transfer case especially if you’re doing it by yourself. Hopefully after reading this you’ll have a good idea of how to install your twin stick.
JKW Twin Stick Kit
Greaseable pivot bolt
With the transfer case removed and grease drained, you will first need to remove the shift rail ball detents. This is what gives your shift lever the “click” when you shift and holds the rails in position. You will need a ¾” socket to remove the poppet plug and a magnet to remove the spring and detent ball. Next you’ll need to drive out two 3/8” diameter freeze plugs. Drive these into the transfer case. We’ll get them out later with a magnet. These holes give you access to the roll pins that hold the shift rails to the shift forks. Look thru each hole with the aid of a flashlight and line up the roll pin with the hole. The roll pin is a 7/32” diameter so you’ll need a punch that is slightly smaller in diameter to drive them out. Be sure to drive them completely out of the shift fork until they drop into the inside of the transfer case. Now the shift rails are ready to come out. You may need to place a punch or rod thru the hole in the shift rail to use as a handle to aid in removing them. Before removing the shift rails it’s a good idea to put a punch or small screw driver in the hole in the shift fork to keep it in place so it doesn’t rotate down out of position. If you should let the fork fall it’s not the end of the world. You’ll need to tip the transfer case over on its end with the front output pointing up. You can turn the input or output shaft to get the yoke back in position for inserting the shift rails. Also keep in mind that you will need to work both rails to the forward most position as the interlock pins may prevent one rail from coming out before the other depending on their position.
I might add that if you think you need to get further into the transfer case to complete the installation, you can remove the big round aluminum cover plate on the opposite side of the case from the front output shaft. Just be aware that you’ll have (64) individual needle bearings to put back in if you choose to remove this cover. Removal of this cover does give you much better access to the shift forks if you should happen to let one fall from its original position.
Freeze Plugs Removed
This is probably a good time to replace the seals around the shift rails. These are NPG #99858. I would suggest buying these from your local bearing supply or industrial supply house as they are usually cheaper than automotive parts house. I might add that most any automotive bearings can be bought from an industrial supply house at a cheaper price than automotive parts stores. The only drawback is you can’t go into your industrial supply house and ask for an 84 Chevy spindle bearing, you’ll have to have a part number.
Now it’s time to remove the PTO cover plate and retrieve the plugs and roll pins. You’ll need a magnetic retriever (magnet on a stick) to get these parts out. You may also be able to get to parts thru the drain hole.
Now you’re ready to put it back together. Before inserting the new shift rails it is a good idea to shine a light down each shift rail hole and make sure that the interlock pins have not shifted to obstruct the path of the rail. These can be pushed back into position with a long screw driver. The long rail is the “front” rail and goes in the hole nearest the front output shaft. I put this rail in first. The short rail is the “rear” rail. It goes in the hole nearest the center of the truck. When inserting a shift rail you can get the roll pin hole close to the correct orientation by “eyeball” aligning the three ball detent notches with the axis of the hole where you removed the detents. Once you get the rail started into the shift fork you can remove the punch or screw driver that was used to hold the fork in place. I used a tapered punch to keep the fork in position. By wedging the tapered punch into the pin hole, I was able to lift the yoke up slightly to align with the shift rail. Now you can look thru the pin hole to check for alignment or the roll pin holes. It may be necessary to lightly tap the rail in with a brass hammer or mallet as the new rail will be a slightly tighter fit than the old worn rail you just removed. I used electrical tape and taped the roll pin to the punch so it could be inserted thru the case to the yoke.
Plugs and Roll Pins Removal
With the shift rails in, let’s put the sticks on and check out the shifting. Start by putting the ball detents back in. It’s a good idea to add some thread sealer to the poppet threads. The poppet has gasket from the factory but it’s probably not reusable. Then install the rail brackets as shown in the picture with the 5/16” diameter roll pins provided with the kit. Notice the orientation of the split in the roll pin.
Roll Pin Taped to Punch
A wise old man once told me that roll pins should be installed in a manner to where the load on the pin would not collapse the pin by closing the gap. I don’t know how true the advice is but it was free. Anyway, position the shift levers and install the new pivot bolt. You’ll need a 1-1/8” wrench, socket or an adjustable wrench for the pivot bolt. Now install the freeze plugs. These can be expanded slightly with the ball end of a ball pen hammer for a more snug fit. Add 90wt grease and you’re ready to put the case in the truck.
Rail Brackets Installed
Roll Pin Orientation
- JKW Off Road