I got a 2001 4X4 blazer with the automatic 4x4 button. While I'm in 2 HI the button light is steady and everything functions almost normally except that while in 2 HI my front drive shaft will spin when I make the rear tire spin. If I press the 4 LO button the relay on TCCM clicks, transfercase makes shifting sound and it will be in LO range BUT front wheels don't spin but shaft does and the button blinks. Basically same thing in 4 HI. If you push 2 HI again it will click relay, shift sound from transfercase, 2 HI button lites steady but again the front shaft will spin if rear tire spins. Am I on the right track to check the front axle cable and vac actuator or could it be something in the transfercase? oh and I took the TCCM out and cleaned the terminals on both plugs and they were corroded some, didn't help.

 

If the light does not illuminate into your selected mode/range, the encoder motor did not fully complete the shift. This could indicate a problem with the encoder motor or TCCM. The most common cause is an encoder fault.

One thing to note with the NV236 (4-button) transfer case. The viscous clutch is preloaded. The front driveshaft will always spin regardless of what mode you have selected.

Another quirk of the NV236 transfer case is that a Tech 2 or equivalent scan tool is required to access the TCCM and read the codes.

 

I have had trouble with my vac actuator before and my cable to the differential but usually I could mess with them and it would work but not this time. This is what my terminals looked like before I cleaned them.

 

That definitely could do it. Did cleaning them fix your issue?

 

no, its still doing the same thing. I'm going to check to make sure the differential is engaging and try any of the "easier" stuff. Back when I first got it it was difficult to get the actuator to pull the cable just right so maybe that's the best place to start. I got the actuator re-located beside the battery instead of under it so it will be easier to mess with it. The vacuum is pulling the cable but the mount may be bent some and just not pulling it far enough.

 

Have someone wiggle the front tires while u squeeze on the actuator. Maybe it's just not locking right

 

FINALLY got my 4 wheel drive working again! I had just quit on it because I couldn't figure it out. I actually built a vacuum cylinder to replace the rubber one that rots or ruptures but it still wouldn't engage. I got up under it and checked around but didn't find anything really not working. I unplugged the differential switch and checked to see if it might be bad and it wasn't closing when transfer case shifts. i jumped across the wires and the LED on the button quit blinking, so now I knew the diff wasn't shifting all way in. I removed the 3 bolts holding the cable to chunk and wiggled the shifter & it was evidently stuck, because it started shifting! I put the bolts back in and engaged it again and it shifted all in and LED didn't blink! I tried it out around in the yard going over a couple of hills and the 4 wheel drive is now working. I got to make a few mods to my vacuum cylinder and I'll post some pics. It doesn't have any rubber boot or rubber to rot, took a couple of weeks to design & build but works great.