My 4x4 used to work just fine last winter, however it started to make some strange sounds this winter. The sounds could be described as a low grinding mixed with humming you can feel throughout the cab. Now the blazer is engauging into 4hi/4lo but I do not have any power to the front wheels. 4lo also spins the rear at 4lo speeds.

 

It sounds like the front axle is not being engaged. This could be due to the vacuum actuator that pulls on the cable to the front axle leaking, the vacuum line to the actuator leaking, the other vacuum lines connected to the engine are leaking, or that the gears in the axle that are engaged by the actuator are stripped.

At least in the second gen Blazers (what hear is yours?), a leak in the vacuum lines under the hood will also cause issues with HVAC system actuators under the dash in addition to the front axle not being engaged due to lack of vacuum. This is what happened to me. Fortunately, the fix of replacing all the vacuum lines is not too hard to do.

 

its a 2003 Zr2 on 33's Is the vacuum actuator the little diaphragm contraption under the battery?

 

Yep, the actuator under the battery tray pulls on a cable to engage the axle.

What you can do is see if it moves when you select 4wd. If not, there is a vacuum leak. You also can trace the hose to it to where you can disconnect it and apply a vacuum separately.

Is your transfer case control have three buttons or four with the auto 4wd setting?

I have a link in my signature for checking and replacing the underhood vacuum hoses.

 

4 button Auto/2hi/4hi/4lo
thanks!

 

Hey there, So i replaced the 4x4 Diaphragm Cable Contraption and still no result. its pulling and holding a vacuum I watched the actuator suck in/out going from 2hi/4hi. Anything else to check on?

 

I have never tried this but you should be able to engage the front axle by manually pulling on the cable that goes between the vacuum actuator and the front axle.

If you cannot engage the front axle by doing that, then my best guess is that either the cable is broken, its attachment to the axle mechanism is broken, or the gear(s) of the axle engagement mechanism are stripped.

Do you have any exploded diagrams or a repair manual to help you?

 

Nope im going in blind to this whole thing. Ill check the cable

 

I dont know if this is working correctly might be