1998 blazer, nv233, 3button 4wd. This thing has me stumped. Can someone please help me out! The vacuum and mechanical side works fine. I have it narrowed down to electrical. New tccm, new transfer case motor. Buttons replaced too. But 2hi sticking. I been studying the wire diagram for hours.

 

I would go with the two piece axle shaft is not engaging. Pretty common failure point on these vehicles. Had it happen on my Blazer and put in a one piece shaft and it solved the problem.

 

I second this, it also happened on mine. I had to replace the gears in the diff.

 

what does one piece shaft mean,is that the bravada change over?

 

Thanks guys for the response, the last sentence in my original post is not accurate. Since it only shifted in neutral to 4low and back to 2hi. I grounded pin #13 at the dlc. Got a code of 2 flashs. Wich according to diagnostic chart indicates a tccm fault. The info said it would do exactly what I'm experiencing. Pulled the connector to transfer case motor and tested the 4 channels. Channel p,b,a all showed voltage of 4.92 volts. But Channel c red with white striped wire pin -8 had no power. Then pulled all fuses and tested for continuity on Channel c from motor connector to tccm. Had good continuity and less than 1 ohm resistance.
so it seems the tccm is not sending the 5 volt reference to the shift motor. Troubleshooting info says to replace tccm, but its new from rockauto, dorman #599100.

 

When it go's into 4low the vacuum actuator gets good vacuum and the right front wheel engages and disengaged. I'm starting to wonder if Channel c is for 4hi?

 

Light dawns on marblehead! 😆 per the troubleshooting on this sight. I have determined the new dorman tccm from rock auto is defective out of the box. China parts go figure! Chanel c to shift stepper motor has 2.4 volts, not like the 3 others at 4.92 volts. Troubleshooting says defective tccm. Rockauto is sending me a replacement!!!

 

thats good maybe ,,,,last fall,i fixed my grandsons shift motor with one whack with a hammer

 

Glad it worked! With my luck if i hit mine with a hammer I'd brake it 😆. Mine has over 312k. Original engine. Never been apart.The dash circuit board that feeds the odometer has broken solder joints. Im not fixing it lol! That was 3-4 years ago. So she must have at least 320k. Now!!!

 

I think the grease they put inside dries out and they stick.