I've replaced the actuator under the battery. The actuator cable. The vac hoses. The front transfercase. The transfer case switch on the transfer case... Tested the tccm.. Tested the dash switches and still nothing will engage the 4x4.. It won't engage in 4x4 hi and in 4x4 Lo only the right passenger side tire rotates... I'm all out of ideas at this point.. If Anyone can help if greatly appreciate it.

 

Here is an open vac hose but I don't know where it goes to

 

When you say only the passenger side tire rotates in 4Lo, is that the front passenger side? If it's the front, then your 4wd is working, at least in 4Lo, right? Unless you have a locker up front, only on tire (the one with less traction) will spin. It's the path of least resistance.

If you meant it's the back tire, then yeah, no 4wd. Do you hear the t-case shifting when you shift to 4wd?

 

i belive that hose supplies vaccum to the vent controls and/or 4x4 vacuum switch. I may be wrong

 

I`m agreeing and it may effect your fourwheel also

 

Hose looks a little short (probably torn), but I believe that is the vacuum line that goes to the reservoir inside the driver's side fender (it's hidden very well). Earlier models had a baseball reservoir attached to the hood. Little bit of a pain to re-attach but I explain how I did it at the end of this link https://blazerforum.com/forum/engine...nowhere-75282/

 

what is the reservoir for??? Does it affect the 4x4 system at all?? I just capped it with a screw but I'd like to know if this is why my 4wd doesn't work and yes 4lo only have the front passenger tire that rotates but not the driers. Aren't they all supposed to rotate?! 4hi does not work at all

 

On an open differential, usually only one tire per axle will be driven. Ever see some guy doing a burnout and it just leaves one black mark? They're built like this so they won't bind up when cornering. The outside tire is making a longer arc, and therefore turning more revolutions than the inside tire. If they were directly mechanically coupled (i.e. a spool, or "lincoln locker") The tires would chirp and skip around corners. A limited slip differential uses clutches to tie each side together, but will still allow for "limited slip" during cornering.

This is why people choose to install "lockers" in their diffs. It sucks to have one tire on good hard dirt, and the other in mud, and the mud one is spinning and you are hopelessly stuck!

If your truck will shift into 4lo, and you are driving any/either wheel on the front axle, then the front axle is not the problem; it's shifting fine. Somewhere on here is a thread that discusses a range shift vs a mode shift. IIRC, mode is 2wd to 4wd, range being 4hi to 4lo. I believe since yours only goes from one extreme to the other (2wd to 4lo) the problem is in the encoder motor on the t-case.

I'm sure someone more knowledgeable than me will chime in, but that should give you a little to work with.

 

The reservoir provides a constant vacuum used when actuators engage and disengage on the vacuum system. Your actuator under the battery would't engage or stay engaged if there are any lines on the vacuum system this open. You might also notice issues with cruise control and hvac controls if you don't have a reservoir of vacuum.

If you find your reservoir does have the correct vac line attached you need to refer to a vacuum diagram to properly address this leak unless you don't mind strange hvac behavior and potentially no cruise control.

I had a 4wd issue with the actuator being broken, the lights 4hi and 4low would come on however, the front wheels would never be driven.

Can you clarify if your one of your front wheels move in 4hi or 4low? Here is how I would test this:
(I wouldn't run wheels more than 1 mph for more than 3 minutes as this is unsafe on floor jacks and jack stands and running engines/transmissions can overheat if raced while not moving).
1. Lift up one side of the blazer off the ground so both front and back tires are off the ground a few inches. Chuck both tires on non lifted side to avoid unsafe movement.
2. Turn on car.
3. Release e-brake.
4. Shift tcase into 4hi
5. Shift into drive with brakes on.
6. Release brakes.
Have someone check to see if both wheels turn at same speed. Record yes or no.
7. Press brakes and make sure both wheels stop.
8. Shift into Neutral.
9. Shift tcase into 4low
10. Shift into Drive.
11. Release brakes.
Have someone check to see if both wheels turn at same speed. Record yes or no.
12. Make sure both wheels are stopped with brakes before shifting to park. Completing test.

Two positive results from the above makes me ask this question because this is normal for non-locking differentials:
Can you clarify what you mean by 4hi doesn't work at all?

 

I would definitely re-attach the hose with new 5/32 hose. As stated the reservoir holds the needed vacuum for "instant on demand" vacuum so you don't get a delay (or maybe even failure?) on your front axle locking or your HVAC doors working. The lines themselves I don't believe hold enough vacuum for instantaneous action.