Looking at the passenger side of the tranny. The plunger is on the endcase near the 5th gear cluster. If you look at a standard DSM tranny in this spot, you'll see an unmachined hole where the plunger goes (or a plug, not sure which) - they used the same cases for the switchable and standard trannies.
A closeup of the plunger/bolt/bracket.
A front view of the plunger, with the FWD/AWD sticker clearly visible. Just remove the bolt and pull the bracket off of the plunger, it is spring-loaded and will extend to lock the center diff for FWD.
I was putting this tranny/transfer combo in my 90, and somewhat panicked when I saw that the selector lever on the tranny was much longer on my 90. Many people note having to change shifter cables in this case - I'm not so sure this is necessary. In my case, I removed the rubber cover on the selector arm pivot and found a nut. I removed the nut/lockwasher/washer/spacer, and just slipped the shorter arm off, then bolted the longer 90 arm on. It shifts fine.
A side view of the original, shorter, JDM selector arm next to the longer 90 arm - note the side offset is the same, only the length of the pivot arm differs.
A closeup of the shorter JDM arm transposed on the longer 90 arm - you can see they differ by at least 1/2". If you used the shorter JDM arm, the distance between 1-2, 3-4, and 5-R would be much smaller, leading to high risk of shifting into the wrong gear. I happen to like the left-right distances between gears, and have shortened the front-back by installing a Mofugas Short Shifter, so I did use the 90 arm.
Driver's side view of the switchable transfer case. If you look at a standard DSM transfer case, you will again see an unmachined hole/plug where the plunger is on the switchable case.
Rear driver's view of the plunger/bracket/bolt.
Closeup of the sticker, as shown on the bottom of the transfer case. As you can see by the sticker position, when you remove the bolt/bracket, the plunger retracts, releasing the internal shafts, allowing the gears to freewheel.
JDM CAPS diagrams of the internals of the center diff (NO, I don't have the JDM CAPS, the pics are courtesy of RRE). You can see by the diagrams that the center diff is driven off of a different gearset on the switchable tranny compared to a standard DSM tranny.
JDM CAPS diagrams of the internals of the transfer case (NO, I don't have the JDM CAPS, the pics are courtesy of RRE).
Now here's the weird part. My Switchable lost 3rd and 4th gear a while back, and when I took it apart to see if it was the shift fork, the parts looked nothing like the ones in the above JDM diagram.
Here is the tranny with the end case off. First thing I noticed is that the retainer for the 5th gear synchro is different. Rather than using a wave spring that is mounted on the endcase, it uses a steel plate that is bolted down under the 5th gear retaining nut.
The 5th gear retaining nut removed, retaining ring out of the way. This tranny does not use a synchro on both sides of this gear like the US tranny does.
Retaining ring out of the way.
The end case - note there is no wave spring mount or wave spring like there is in a standard US tranny.
A closeup of the clearance between the VC shift fork and 5th gear - the fork is ground to clear the gear. 5th gear is a bit messed up, I have replaced it with a spare.
The VC shifter ring, at the bottom of the VC.
The VC shift fork - when the bolt/bracket are installed on the endcase, it pushes the shift fork down, pulling the shift ring down, disconnecting the inner and outer sections of the VC from each other, allowing normal VC operation. When you remove the bolt/bracket, a spring pushes the shift fork up, and the shifter ring teeth engage both the inner and outer sections of the VC, locking them together for 2WD operation.
VC and shift fork mechanism removed from the tranny, bottom view.
Shift fork and ring lifted up, you can see the engagement teeth in the ring.
VC - here you can see the gears welded to the inner and outer "halves" of the VC. When the shift fork is released, the ring engages both of these gears, locking the VC.
Once I had removed the midcase from the tranny, the internals looked exactly like those of all my other 90 AWD trannies, so I'm hoping John Shephard can to one of his magic rebuilds to it.
I never did find out why 3rd and 4th are gone. When I drained the tranny, the fluid was completely clean, still clear red (Redline MT90), no metal dust at all (I had only run it for 3 months before losing 3/4). When I opened up the tranny, there were no metal bits inside. The 3/4 shift fork was fine. I put the tranny back together, stuck a clutch disc on it, and rotated it in 1-5 and R, and it spun the output shaft and front diff fine. But as soon as I threw a transfer case on it, the increased friction made 3 and 4 freewheel, I could spin the clutch disc while holding the transfer case yoke in 3 and 4, but the clutch disc would not move at all in 1/2/5/R. The best I can tell is that the 3/4 gear cluster shaft sheared clean somewhere and when 3 or 4 are engaged, the 2 halves rotate independently. When I had both gear clusters out of the tranny, I could not twist the ends opposite each other at all, so it must have something to do with the position of the gears. I'll let Shephard figure it out ;-)