The neutral safety switch (NSS) is a fairly well-known problem area on Jeep AW4 transmissions. When you have a problem with it, it usually manifests itself as reverse lights that don't come on, or as a no-start condition because the Jeep doesn't think the transmission is in Park. Making things even worse is the fact that the NSS typically sells for USD$200 at some online sites, and into the $400 range if you buy locally. That's a ridiculously high price for something that is basically a rotator arm and a few copper contact strips. Its job is to indicate when the transmission is in Park, Neutral, or Reverse.
Fortunately, the NSS is quite easy to take apart and rehabilitate. So let's see how it's done:
The blue square indicates the NSS module.
The green square indicates where one of the zip ties are located. There were three I had to cut.
The red square indicates the retaining bolt that holds the NSS to the transmission.
The first step is to disconnect the NSS harness. Its connector is located near the transmission dip stick.
To make it easier to route the harness during re-installation, I tied a string to the connector before pulling it down. As it turned out, the string wasn't needed. For whatever reason, Chrysler chose a very weird route for the harness. When I re-installed, I ran the harness around the outside of the dip stick tube, rather than trying to run it between the tube and firewall as it was originally done. This was far easier and made more sense to me.
Before I was able to pull the harness down under the Jeep, I had to cut the zip ties holding it in place. This will require some hand gymnastics. These side cutters worked pretty well but a pair with longer handles would've been useful.
After I cut the zip ties, I made sure the transmission was in Neutral.
Then I removed the retaining bolt. You can see that there is some room for left/right adjustment. More on that later.
The next step is to loosen the nut on the shifter shaft. Under all that grime, you can see that there is a lock washer under that nut.
The lock washer has a few bendable tabs that are preventing the nut from loosening. I bent the tabs flat and then loosened the nut, but I left it threaded onto the shaft.
Next, I inserted a flat bladed screwdriver under the nut, and used the edge of the transmission pan as a fulcrum. This is an important step because the NSS module needs to slide straight off of the shaft. It can't be twisted off. By prying on the nut, I was able to exert side ways pressure and the NSS module easily slid off the shifter shaft.
This is about as far out as I could slide it by prying. I pulled it the rest of the way with my fingers.
With the module removed, I then pulled the harness all the way out. Of course, the string came along with it. But like I said before, it turned out that I didn't need the string after all.
So this is the little bugger that was stopping my Jeep from starting. Doesn't look like it's worth $200, does it?
Here it is with the nut removed (you can see the lock washer more easily, now).
And here it is with the rubber washer removed.
I sprayed it with brake cleaner and scrubbed it with a wire brush. The next step is to remove those six Phillips head screws.
With the screws removed, I very gently pulled apart the case halves. I was concerned about the two spring-loaded contacts shooting out. But the springs were so gummed up with old grease that the contacts didn't move very much at all. Inside I found some old grease and a bit of corrosion.
The springs and contacts I'm referring to are in the rotating contact arm (red box).
The arm is easy to separate from the case half.
I very carefully removed the spring loaded contacts, and then the springs beneath them.
Here are the two springs and their contacts.
I used more brake cleaner and some scrubbing with my wire brush to clean off all the old grease and other crud. Then I polished the copper contact surfaces with emery cloth and then sprayed them with contact cleaner.
I smeared a bit of dieletric grease on the slots in the contact arm and inserted the springs.
Then I smeared some dielectric grease on both case halves, as well as along the case's sealing groove.
Then I put the contact arm back in the case half. Notice how its contactors are sticking out much more than when I first opened it up. The springs are no longer gummed up. After this, I put both case halves together and re-installed the six screws.
Installation is, as they say, the reverse of the removal process.
When I slid the NSS back onto the shifter shaft, I inserted the retainer bolt and hand-tightened it. I did the same with the large nut. Then I ran the harness back up along the firewall and re-connected it. Then, with the transmission in Park, I successfully started up the Jeep. The first test was passed. When I shifted into Reverse, the reverse lights came on. Second test passed. Finally, I shut it off in Neutral and tried to start it up again. No start. Fail.
So I loosened the retaining bolt, rotated the NSS clockwise a little bit, and re-tested. Start in Park, check. Reverse lights in Reverse, check. Start in Neutral, check.
The large nut doesn't require much torque. I made it just a bit tighter than hand-tight. Then I bent the locking tabs up to prevent the nut from coming loose, and zip-tied the NSS harness back into position. It took me about two hours, working at a very relaxed pace and taking pictures.
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