4 wheel drive problem

We took our 1995 Blazer in for a trade-in estimate yesterday and the guys came back and said that the 4 wheel drive wasn't working. Sure enough, when I put it in 4 paw the light on the console doesn't come on in 4 high or 4 low. When I put it in 4 low, you can hear the transfer case whining like it's in 4 low but the front axle doesn't appear to be engaging.

It worked fine before I did some maintenance on it a while back, but never tried it after I relaced the upper and lower ball joints and an idler arm.

Anyone have a recommendation on what I should check ? What could I have accidently disconnected or messed up when I relaced the ball joints ? We didn't have the axles out. Is there a sensor or something ?

I would appreciate any suggestions ! Not too far off from winter here in Minnesota !!

Thanks !

What component makes the front hubs engage ? Since it appears that the transfer case is engaging, I'm assuming that whatever tells the hubs to lock isn't working.........

Changing ball joints should have no effect on the 4WD.

You need to check to see if the front differential is engaging. Secondly, You need to check the actuator on the transfer case.

I will assume you know how to do this.

"You need to check to see if the front differential is engaging"

Actually, I don't. Can you give me an idea ?

Check the vacuum actuator for the 4WD.

Check the vacuum actuator for the 4WD.


Is this for the transfer case or the front hubs ? Can you tell me where it's located ?

Sorry for all the questions, but I'm a Mopar man......

O.K., I just went out and found (I think) the vacuum actuator under the battery. The cable going to it resembles an old speedometer cable but is much smaller. It has a solid core with a stiff coil type wire sheath around it covered by plastic. The cable has a spot where the battery acid (over the years) has burned off the plastic and the wire coil in one spot abound 1/4". The solid wire inside is still intact. I made sure it wasn't grounding out to the fenderwall and srtarted it up and engaged the transfer case, but still no go.

I didn't yank the battery but was curious, is there vacuum lines that could become disconnected ?

Suggestions ? Would you folks recommend replacing the vacuum actuator & cable as a starting point ?

Thanks for all your help ! I really appreciate it !

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THANKS !

You think that cable is an issue ? I could email you a digital picture of the spot in question or post a picture here.......

It is usually the vacuum actuator that is the problem or a rubber tube supplying the vacuum has cracks.