OK. So did some searches here. Started to do testing. I WAS going to pull out the TCCM and check the connections, however when tryng to take my kick panels off I found that my dash panel is brittle as hell from this Texas heat. It started to crack around the light switch. So left that. But I attempted to check the shifting anyhow. As my pics I have the 4 position switch. not buttons. Well I switched from 2hi to 2awd. I couldn't hear anything. So I switched to 4hi. I could hear something engage and the light for 4hi blinked. But it stayed lit on 2hi. So I put it in neutral and tried to shift to 4lo. I could hear the clunk and felt it kind of jerk the truck. So I switched back to 4hi and again the clunk and it jerked. So it seems to WANT to engage. I'm going to use my shop jack and lift the back end and see if the 4x4 actually engages (prob tomorrow) but looks like I'm going to have to have it scanned to find why the service 4x4 light is actually on. My old OBD2 scanner won't do. Any thoughts though? for now I'm gonna focus on my old friend the intermittent wipers.

 

Being a GMT360/370 truck (Trailblazer) it will be different than the s-series trucks that are most commonly talked about here. Having had one quite a while ago, I can try to help. The 4wd system still operates similarly to the s-series trucks in that the front axle has a disconnect in it which is an attempt to remove parasitic drag on the drivetrain when in 2HI. This disconnect has a feedback sensor that tells the TCCM the status of the connection (engaged or disengaged). If it does not see the proper status within a certain period of time, it will revert back to the previous mode. Reading the codes from the TCCM should give you insight into what is going on, but it is a somewhat common issue with all of these trucks.

Replacement actuators as well as the entire engagement housing are available. The actuator is VERY easy to replace requiring only an 8mm socket with a 6" extension on your ratchet and can be done by simply turning the front wheels all the way to the right. The engagement housing is quite a bit more labor intensive as the axle shaft has to be removed to replace this piece. The GM part number for the actuator is 12471631. There are aftermarket actuators available for >$50, but I am not sure as to the quality of these cheaper alternatives, but it comes down to what you can get.

 

Yes, thank you. That sums up good what I've been reading. I can see now the changes are significant from the S10 blazer to the TB's. Now having both it is noticable. Yeah, I can see that having those codes read will be necessary and I believe that the actuator is the culprate. But not just going to throw cash at a problem. My old Jimmy 4x4 was easy. This is a learning curve. But since the rest of the truck is running fine it's not a priority. So I'll look into who will read the codes cheapest (we have a couple shops in town) and take it from there. Overall I like the TB. I'll let this go for now and will post back when I get more info. For now gonna focus on the Blazer's P0420 (yeah I know, common)

 

I am SOOOOO majorly disappointed. So I went yesterday to the bucket sale and picked up a spare tccm and the actuator sensor for the trailblazer. Well today I went to swap the actuator. come to find out that BOTH the cv joints have been removed and the front transaxle ends are wide open. This is very concerning to me. Who knows what was going on with whoever did this. It could be any number of reasons. I can't even begin to think why someone would do this. Could the transaxle be locked up? I don't know. This is on me for not looking under there when I bought it. I didn't buy the truck FOR the 4x4. I only bought it for the truck itself. But I'd expect at least some semblance of together. Even if it's non functional. Because now my question is did leaving those cv joints out maybe damage the internal mechanics of the transfer case? If I get replacement cv joints and put them in should I check for anything else. Aside from obviously replacing the fluid. I mean, my god, WHY would someone DO THIS?