Does anyone have a pic of what this looks like, so I know what I am looking for? I have a vacuum gauge and can check vacuum if needed, I just don't know what it looks like?

 

In that reply, switch = actuator. There are plenty of pictures of this spread around on the forum. It is a black plastic vacuum diaphragm with a vacuum hose in one end and a cable attached to the other end. Hard to miss.

 

Heres a picture of the actuator i posted it in another thread a while back but here it is again. Like its been said its under the battery tray. just put your finger on the end of the hose and see if its working. Also check the actuator to make sure its not torn or anything. You will want to pull on the cable also to make sure its not seized up from being rusted or anything also. good luck

 

Ok, followed the vacuum line from the actuator under the battery, to the switch on the cowl above the engine, back to the T on the driver's side of the engine bay. I didn't see any visible breaks in the line. When I put the truck into 4HI, or Auto4, I can hear it "click" under the truck at the front axle each time I switch between 2HI-4HI or Auto4, but the light still keeps blinking unless I put it back in 2HI.

Now in 4LO, I got it to stop blinking, and it drives as if is in 4LO with the very low gearing (didn't take it above 10-15mph), however, it took a few attempts to get it back into 2HI afterwards, and still won't go into 4HI or Auto4. How do I diagnose this without blindly replacing parts?

 

Sorry kgkern, I did not see this latest question.

Your problem sounds like the classic encoder fault. If you have not done so already, get the codes from the TCCM. It may be able to point you in the proper direction. A fairly high feature scan tool is required to pull the codes from the TCCM used in the Auto4wd optioned vehicles.

 

Fixed it, to get the truck running while removing the battery and tray I ran jumper cables from the battery next to the truck to the terminal wires on the truck, making sure the positive side was insulated from grounding on anything.

With the truck running, I pushed 4HI, nothing, like usual, so I pushed in the diaphram on the actuator myself all the way in, and viola! It worked!! I think the actuator was just sticking after not being used for a few months. After that, it began functioning as normal!

Cost to fix $0, Time, 15 minutes.

 

Hopefully the fix lasts and doesn't leave you stranded! Glad you got it working!

 

when you pushed in the diaphram how far did it travel?

 

When I pushed it in, it became flush with the metal lip. Pretty much all the way in.

 

i'm having the same issue with my blazer and mine only travels maybe 1/2inch , definitely not all the way in .