I figured I would share a little how to on how to locate an internal problem with the TC encoder motor. Here is my story below, and following that is my diagnosis, and end successful result. I have gotten loads of info from this site, so I would like to give some of that back. It doesn't appear that anyone has dissected the EM yet. Please not, there are various things that can and will eventually go wrong inside the EM, most are unfixable because they do not part out the unit, but rather buy a new one. But should you have a spare, the parts are super easy to disassemble and re-install. I was lucky to be able to find and fix the problem.
PROBLEM
Over the summer I replaced my 4DW disconnect with the AWD collar gear, and rebuilt the disco, this solved all my problems that I had before. Due to the lack of off road opportunities in MA, we finally got snow this week, and I was able to play around with the 4WD last night. Everything worked flawlessly in 2HI, 4HI, and 4LO. I was screwing around, and switching back and forth to cycle the TC through it's paces.
I then decided to test the Auto function. I felt the TC engage when the wheels started to slip, but it it stuck in 4HI. I try and cycle through the selections on the switch, and the light just flashes for about 6 seconds, and returns to 4HI, no matter the switch position. I noticed that something sounds different on the TC when I select the switch. I think its the encoder motor, the round solenoid/motor that runs when you select the switch. This sounds different, and it doesn't sound like its disengaging the TC. It sounded like its under a heavy load and its trying to work, and makes 2 attempts to switch, then reverts back to its original setting (in this case 4HI). I tried jacking the front off the ground to take the load off, and smacking that motor with a dead blow hammer while switching through the gears and still no joy.
The transfer case, and 4WD fuses aren't blown, and I had a service 4WD light come on after I removed the fuse for 4WD in the back, and it concurrently went back out after I removed and replaced it again. So now theres no service lights, but its stuck in 4HI.
SOLUTION
Since I had the suspicion that it was the EM, I removed it today to take a closer look. I will assume that everyone up to this point can successfully get the EM off the TC. I didn't take any pics of that part. It's very easy, 4 bolts, and the wire harness, and is very openly accessible from the mid undercarriage area. I removed the EM, and because it was under a load, when I pulled it off the TC, there was excess torque stored, and it subsequently put the TC into neutral. I would suggest while you have the EM off, cycle through the 4WD switch, and ensure that the motor turns. This will be easily identified by the gear at the flush end moving slightly.
Once off the TC, the rest is rather simple. There is a plastic/rubber gasket that is on the front, which can be removed by some set clips that must be unclipped. This appears to be a reusable gasket.
See Picture #1
- Picture #1
Next step is to remove the cylindrical cover that houses the actual motor. This has two torx screws. THis cover should pop off of a blue O-ring. THere may be some resistance, as the cover is lined with 4 magnets for the motor. You can now pry at the seam of the motor, and remove it from the planetary gear set. The motor itself is plugged into the power cable housed in the inner wall of the gear sets. Pull the motor off until it unplugs, at this point the plug is the only thing securing it in the housing. Once removed, there will be a thin thrust washer that lays on top of the gears, remove and set aside.
See Picture #2
- Picture #2
At this point, you can see inside the planetary gear set-up. There are 4 sets of reduction gear, ranging from small at the top, to big at the bottom. These are easy to remove, as they are stacked in order of size. As you can see, for all 4 layers of gears, there are 4 gears, and one plate that they all sit on, on a post. Beneath this plate, is another fixed gear that sits inside the next stack of 4 below it. This will be become more clear once you open it up. Keep all 4 sets of gears/plates set aside once you remove them.
See Picture #3
- Picture #3
While taking the gear sets out, you should be able to see whether or not there is something wrong/broken/cracked, or otherwise keeping the innards from moving. In my case, everything moved as it should have, all the way down to the base gear. I put a little bit of grease back on each layer, and reassembled in reverse order.
See Pictures #4-6
