My ZR-2 will not shift into 4 wheel drive low high or auto. Its a 4 button style. I have replaced a couple of frail looking vacuum lines but that did not do the trick. What do I need to look for next to remedy this problem?

 

Because it is so easy to do, check all of your vacuum lines closely and not just visually, before moving onto other causes.

The other things to check would include if the transfer case is being engaged or not. Then if it is the front axle that is not engaging.

 

Thank you for your reply. What is the best way to check the vacuum lines...visually or some other way? When I try to shift to any of the 4 wheel settings the lights just blink. When a push the two wheel drive button I can hear a shifting noise under the car. My guess is that that is the transfer case on the front axle. Is that a good noise to hear?

 

The best way to test the vacuum lines is with a hand vacuum pump. But going over them with your hands to search for ones that are brittle or cracked will work too. Be sure to check where the hoses attach to the nipples.

A common issue is that there is a vacuum reservoir that is a but hidden having its hose leak or fall off.

I have a thread in my signature that shows the diagram for a 4-button transfer case.

For the transfer case, do you hear any clicking from the passenger side kick panel when press the 4-hi button? This would be coming from the transfer case control module (TCCM). You should only hear a click or two. If yoy hear repeated clicking or none at all, the issue could be with it. However, if you are hearing engagement if the transfer case as I think you are, then the TCCM could be fine.

 

Thank you again for responding. I will check all of the vacuum lines for brittleness. I do not have a hand vacuum. Where can I pick one of those up if I need one? When I switch the the trans from attempting to go into 4 wheel high, low or auto which only gives me a blinking light. When I push the button to switch back to 2 wheel is I hear the click and it sounds like it is coming from below the pax side. It only clicks once. That is a good thing correct?

 

You are very welcome.

From personal experience and from what others have posted, the under-hood vacuum lines tend to start failing when the trucks get to about 15 years old. The sneaking thing is that they can look fine when in fact they are not and are instead leaking.

As for a hand-held vacuum pump, you can often borrow one from a local auto-parts store.

As for the TCCM, you should only hear one click when a change in the transfer case configuration is called for.

Another issue that can arise is with the engagement of the front axle. There is a vacuum actuator under the battery tray that pulls on a cable that engages a gear on the front axle. Even with the transfer case engaged correctly, without the passenger side axle engaged to the front differential, you would find that you effectively have no 4-wheel drive. Mechanically, the passenger side of the output of the differential is free to spin as it the passenger side tire is on ice with the drivers side on dry pavement.

Here's the link to the full thread on replacing the vacuum lines in a 4-button blazer: https://blazerforum.com/forum/2nd-ge...replace-95425/