Okay so I take my truck offroad sort of often where low range is pretty much 100% necessary(slow N rocky), but my low range is decently intermittent. Now that the temps have gotten colder I cant get it to go into low at all. Im scared to try it anymore in fear of getting it stuck in low range which has happened before. Goes into 4hi no problem everytime(I also have posilock), but im pretty much looking for suggestions on parts I should look into replacing. Thanks. I have 4 button 4wd.

 

My encoder motor went out. 4hi was fine but no 4lo. I had to wiggle the shifter when I was in Neutral after pushing the 4lo button because my shift linkage is a little off before it would go in or out of 4lo. Check vacuum lines for slow leak. Mine is a 3-button 4WD.

 

also if it helps when I did get it stuck in 4lo about a month ago, I got it out by disconnecting the battery, then it popped out first try. I have used it probably 6 times since then with no problems. Only thing that changed is now its cold.

 

This really helped me understand the 4x4 system and what to test/look for:
https://blazerforum.com/forum/tech-a...ill-help-7180/
Go down to post 3 or 4, and it give the breakdown of issues, common problems, and fixes.

 

That link is pretty good for the NV231 manual shift transfer case, and the NV233 electric shift transfer case. However, the NV236 transfer case, (4 button switch) has electric shift, but it also has Auto 4WD. Operation, diagnosis, & repair procedures are similar, but not the same.

When you initially turn the ignition to the run position, do the 4WD switch lights blink?
When you select 4LO do the switch lights blink?

Is so, how many times do they blink?

 

I will check for the ignition in the run position, but yes the light blinks when selecting low, and works going into 4hi seemlessly.

 

switching the truck to on all the lights come on then 2hi remains lit as expected. Went to try it to check blinks and it went into low range and came back out no problems, but in the past I believe it just blinks nonstop for maybe 10secs then goes back to 4hi.

 

If it goes into 4HI and stays there, the vacuum switch on the firewall is supplying vacuum to the actuator under the battery, and the actuator is engaging the right front axle. That narrows down the possibilities

Check the connectors at the TCCM and at the encoder motor. Make sure there is no corrosion and that the pins are tight in the connectors.

EDIT: The 10 seconds of blinking is the TCCM waiting for a response from the encoder motor.

 

I have posi lock so the actuator is bypassed. I will check those connections, and try it out a couple more times. Shouldnt need it in the next month so weve got some time here. hi is fine for snow.

 

When you installed the posi, how did you deal with the axle engagement switch? The TCCM must see the correct activity from the switch when you shift in and out of 4WD.