Push button 4WD transfer case won't shift to 4HI/4LO

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GT80

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First post here. I've scoured this forum for a solution to my problem but can't find any threads with this particular issue. Truck is a 98 model with push button 4wd. NP 243 C t-case.

When I try to engage 4HI or 4LO, I hear relays clicking and I sometimes get a clunk from the transfer case, the lights flash a couple times, but then it reverts back to 2HI.

Here's what I have done so far. I checked the TCCM for codes and only get DTC 1. I assume that's from all my battery disconnecting and fuse removal. (edit - I cycled the ignition switch 5 times and got rid of this code, so now there are no trouble codes.)

I replaced the switch on the top of the transfer case since it was a cheap and easy part. That didn't help. Here's where things get strange. I then replaced the encoder motor on the t-case. When I got the new motor, the paperwork said that it was shipped in the 2HI position and that if my transfer case wasn't in 2HI I would have to manually shift it to get the tang to align. Well, this motor was in the 4HI position, and even had a plastic keeper "holding" it there (although I can't see how it could move on its own). So I shifted the t-case to 4HI with a crescent wrench and installed the motor. When I turned the key on, the light on the 4HI dash switch was lit and I thought great, I should be good to go. Well, then the t-case shifted beautifully between 4HI and 4LO, the actuator engaged the front differential and everything worked great EXCEPT now I couldn't shift out of 4WD to 2HI. Another issue was when in 4HI, when I shifted to reverse, I got a grinding noise from the t-case. What I found when I pulled this motor back off was that when in 4HI it had the tang on the t-case turned a few degrees toward 4LO so I assume that's why it was grinding. Also, the plastic keeper it was shipped with wouldn't align anymore.

So, I got a reman'd Delco encoder motor. This one was in fact shipped in the 2HI position. I installed it and still had the original issue. Won't shift out of 2HI. The last thing I did was try a new TCCM and that didn't help. Same issue.

Any more ideas? I've basically tested/replaced every electronic component I know of in the 4WD system except the dash switches. I assume the switches are OK because I hear relays clicking and lights are flashing. Is this a bad assumption?
 
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b454rat

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Kinda sounds like the t-case itself is sticking. Maybe find a trail or somewhere to test the 4wd out. Drive around in hi, then go back to 2wd, then low. Might just need to get motivated lol.
 

GT80

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Kinda sounds like the t-case itself is sticking. Maybe find a trail or somewhere to test the 4wd out. Drive around in hi, then go back to 2wd, then low. Might just need to get motivated lol.

At this point, the only way I can get it into 4wd is to remove the encoder motor and turn the tang with a crescent wrench.
 

b454rat

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I had one that the motor was bad. I put a good used one in, but seemed to stick at first. I would drive it around the yard in 4 hi, go out in the road in 2 hi, then back in yard in 4 lo. Other than that, I'm out lol.
 

Supercharged111

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Remove the tail shaft housing the snap ring is probably broken.

If that is the case, there is an upgrade that eliminate the clip. Can you hear the actuator in the front diff doing it thing too? That's what took a dump when my truck refused to go into 4wd.
 

GT80

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If that is the case, there is an upgrade that eliminate the clip. Can you hear the actuator in the front diff doing it thing too? That's what took a dump when my truck refused to go into 4wd.

There's no problem with the front actuator. The issue is in shifting the transfer case to/from 4wd, which I can do manually no problem with a crescent wrench, but the encoder motor won't do it.
 

GT80

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No one has had this particular issue? I'm at my wit's end!! I so wish my truck was manual. Push button is nice until it ***** the bed.
 

GT80

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Reviving this thread. I gave up on it but now I'm trying to figure it out again. The only change since before is the dash switches are new now, but obviously that didn't fix it either. So can anyone tell me what the TCCM logic is? Maybe then I could figure out why it attempts to go into 4wd but then reverts back to 2HI.
 
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